The founder of Zion's Watch Tower Charles Taze Russell made the following statements and now directly contradict new information by the organization

The modern-day organization of Jehovah’s Witnesses began at the end of the 19th century. At that time, a small group of Bible students who lived near Pittsburgh, Pennsylvania, in the United States, began a systematic analysis of the Bible. They compared the doctrines taught by the churches with what the Bible really teaches. They began publishing what they learned in books, newspapers, and the journal that is now called The Watchtower—Announcing Jehovah’s Kingdom.

Among that group of sincere Bible students was a man named Charles Taze Russell. While Russell took the lead in the Bible education work at that time and was the first editor of The Watchtower, he was not the founder of a new religion. The goal of Russell and the other Bible Students, as the group was then known, was to promote the teachings of Jesus Christ and to follow the practices of the first-century Christian congregation. Since Jesus is the Founder of Christianity, we view him as the founder of our organization.—Colossians 1:18-20. Source

Charles Russell was a sincere man who sought to understand the scriptures and endeavored to emulate the form of Christianity practiced by the very early followers of Jesus. He was not inspired by God nor infallible. He made mistakes and got some things wrong. His religious views and beliefs did not all become clear to him in an instant but developed over many years.

Therefore your question is based on a faulty premise. Russell is well known for teaching that Michael is in fact another name for Jesus.

In fact, as can be seen in the book “The Time is at Hand”, written just 10 years after the Watchtower you cite in the first paragraph of your question, he states that Michael is our lord Jesus Christ.

This shows that Russell adjusted his thinking on the identity of Michael the Archangel. This was not a case of new light voiding old light, but rather a case of improving the accuracy of his own biblical knowledge.

Russell was from the earliest anti trinity. Did not believe Jesus was almighty God. The “new light” is greater understanding of the word proskyneo and determining that a distinction needed to be made between the levels of adoration given to Jesus and Jehovah. The word worship in modern language is associated with highest level of honor/adoration. This can only properly be directed toJehovah. Still a very high level of adoration and honor is rightfully directed toward Jesus thus the word obeisance was chosen to express high honor while worship is used for highest form.

Like Mr. Russell Jehovah’s Witnesses continually study the scriptures and are comfortable with adjusting when it becomes evident that a previously held belief is not in harmony with the entirety of biblical understanding.

As for the statements from Russell and others who lived after him indicating that we should worship Jesus and that the angels worshipped Jesus, this is resolved by a deeper understanding of the Greek word proskyneo and the varying degrees of adoration it can express.

Unger’s Bible Dictionary says that this word literally means to ‘kiss the hand of someone in token of reverence’ or ‘to do homage.’ An Expository Dictionary of New Testament Words, by W. E. Vine, says that this word “denotes an act of reverence, whether paid to man . . . or to God.” In Bible times, pro·sky·neʹo often included literally bowing down before someone of high stature. A full discussion of worship is found in this article.

We believe that only Jehovah is worthy of the very highest form of worship as the eternally existing, uncreated Almighty God. Our “proskyneo” toward the Son of God is of a lesser degree. For that reason, we use the word “obeisance” for proskyneo directed to Jesus and use the word “worship”, when context indicates the most reverent adoration, that is for Jehovah alone.

Since none of Jehovah’s Witnesses are inspired nor infallible, there have been and will continue to be a need for adjusting and fine tuning our eschatology as we understand more accurately the inspired word of God.

Here is what C.T. Russell said about "NEW LIGHT":

“If we were following a man undoubtedly it would be different with us; undoubtedly one human idea would contradict another and that which was light one or two or six years ago would be regarded as darkness now; But with God there is no variableness, neither shadow of turning, and so it is with truth; any knowledge or light coming from God must be like its author. A new view of truth never can contradict a former truth. “New light” never extinguishes older “light” but adds to it.” Zion’s Watch Tower 1881 Feb pp.3, 188

This is undoubtedly true. Something taught is either God’s truth or it was never God’s truth to begin with. Russell believed he spoke the truth. And so did the men who followed Russell after he died:

“Jehovah God commands all to worship Christ Jesus because Christ Jesus is the express image of his Father, Jehovah, and because he is the Executive Officer of Jehovah always carrying out Jehovah's purpose (Heb.:3-6)." (15 November 1939 Watchtower, page 339)

Then, in January 1954 that teaching was dropped. From that point forward “new light” contradicted and replaced what had been previously perceived as God’s truth:

“Jehovah's Witnesses say that it is unscriptural for worshipers of the living and true God to render worship to the Son of God, Jesus Christ." (1 November 1964 Watchtower, page 671)

“Reverent adoration should be expressed only to God. To render worship to anyone or anything else would be a form of idolatry, which is condemned in both the Hebrew and Greek Scriptures. Accordingly, true Christians do well to direct their worship only to Jehovah God, the Almighty." (8 April 2000 Awake! pp 26-27)

On page 13 of the 15 September 2010 Watchtower this claim was made by the men who govern the organisation: “The Governing Body publishes spiritually encouraging literature in many languages. This spiritual food is based on God’s Word. Thus, what is taught is not from men but from Jehovah."

The Governing Body must therefore believe that it was Jehovah himself who informed them that Jesus was a created being who must not, under any circumstances, be worshipped.

For what it’s worth, they stopped using the expression “new light” a while ago. They now say they are the recipients of “increased light”. This is based on how they apply Proverbs 4:18 which says:

The path of the righteous is like the first gleam of dawn, shining ever brighter till the full light of day.

Edit: Regarding the teaching that Jesus is Michael the archangel and in response to the OP question asking what new light was received and from where it came, I found this quote from the 15 September 1958 Watchtower article ‘Who is the Archangel Michael?

All relevant scriptural testimony unites to prove that Michael is none other than Jesus Christ, both before he became a man and after his ascension into heaven” (page 559).

Here is another quote, this time from 1974:

"Who, though, was the son whom God chose to be born as a perfect human creature? ...He has rightly been called Michael the Archangel. His life-force having been transferred to Mary's egg cell by Almighty God's power that overshadowed Mary meant that he, Michael, disappeared from heaven. By human birth from Mary, the Jewish virgin, he was to become a human soul." (God's Eternal Purpose now Triumphing, 1974, pp 137-138)

I then searched through the oldest Jehovah’s Witness publication I have – the 1946 book ‘Let God Be True’ – but was unable to find any mention of Michael the archangel, let alone any suggestion he was Jesus before he came to earth or after he returned to heaven. However, in Chapter 3 paragraph 4 on page 35, it says that Jesus was the Word, or Logos, of God.

From there I looked at the 1986 book ‘The Truth That Leads To Eternal Life’. In Chapter 6 under the heading ‘Prehuman Existence’ it say that before Jesus “was born on earth as a male child he served in the heavens, where he was known as “the Word,” God’s spokesman.” No mention of Michael the archangel or any suggestion that is Jesus’ name in heaven (pre or post human life).

I have spent hours searching on the official jw.org website to find any pre-1958 reference to Jesus being Michael the archangel. The problem is that the new web site does not give access to old literature. If Russell said he believed Jesus was Michael the archangel then why would he say Jesus should be worshipped? The Bible specifically says angels must not be worshipped.

So when did the Witnesses first say Jesus was Michael the archangel? Was it Rutherford who came up with this new teaching after Russell died in 1916? Does anybody know? And what “light” caused them to stop worshipping Jesus and merely give him obeisance? Perhaps we should allow Russell to have the last word as he explains why they got things wrong in the past:

“Did the Lord tell us that we would be taken [to heaven] then [1 October 1914]? No. What did He say? His Word and the fulfilments of prophecy seemed to point unmistakably that this date marked the end of the Gentile Times. We inferred from this that the Church’s ‘change’ would take place on or before that date. But God did not tell us that it would be so. He permitted us to draw that inference; and we believe that it has proven to be a necessary test upon God’s dear saints everywhere.” Source: 1 February 1916 Watchtower

I don’t know if Jehovah’s Witnesses would agree with that view, but it goes some way to explaining why changes have had to be made over the past 100 years.

The organization of Jehovah's Witnesses is guided by the Governing Body.

In contrast to most other religions, the Governing Body does not claim to be inspired or infallible.

The Governing Body is neither inspired nor infallible. Therefore, it can err in doctrinal matters or in organizational direction. In fact, the Watch Tower Publications Index includes the heading “Beliefs Clarified,” which lists adjustments in our Scriptural understanding since 1870.

Watchtower February 2017 p.26 paragraph 12

Therefore, there is no 'magical' or 'divine' inspiration or change of dogmas because there are no dogmas. There are sometimes changes in understanding. Before some things were understood in a different way than now. And maybe in some time in the future, they will be understood in another way. The point is that because the Governing Body does not claim inspiration or infallibility, there is no big conflict if they change the understanding. As imperfect people, they can be wrong. Like mature imperfect people, they can admit when they are wrong, and correct their point of view.

“The Governing Body gives all credit for the success of this organization to Jehovah and the appointed head of the congregation, Jesus Christ. We are just imperfect men trying to follow the lead of Christ and the Holy Spirit.”

JW Broadcast July 2017, timestamp 12:18

So as they are all "imperfect men", there is no conflict or problem, with a change of "light" or understanding, between themselves, or previous members of the governing body, or Mr. Russell, or any other imperfect man. Problems only occur because people and also some JWs expect them to be infallible. It seems a deep desire of many believers to worship or blindly follow human religious leaders. Some people can not imagine having a religion where the leaders do not claim to have divine inspiration. I personally think it is very liberating, that leaders of my religion are aware that they are imperfect, that their organization is imperfect, and that they are not too proud to even keep a list tracking changes in understanding throughout history. In the same video linked above a member of the Governing Body quotes the line: “this is the best imperfect organization on earth.” (timestamp 14:17)

The topic of the new understanding of the identity of the Archangel Michael is addressed in the Watchtower 1984 12/15 pp. 26-29 ‘Michael the Great Prince’—Who Is He?

For many years Jehovah’s Witnesses have taught that Michael is a heavenly name for the only-begotten Son of God, who was named Jesus while on earth. However, most other religions view Michael as one of several archangels, as if there were more than one archangel.

More specifically in this paragraph.

"We learn from Jude that Michael had the post of archangel. In fact, he was the archangel, since no other archangel is mentioned in the Bible, nor does the Bible use “archangel” in the plural. “Archangel” means “Chief of the angels.” (Thayer’s Greek-English Lexicon of the New Testament) Among God’s spirit servants, only two names are associated with authority over angels: Michael and Jesus Christ. (Matthew 16:27; 25:31; 2 Thessalonians 1:7) This, too, argues that Jesus and Michael are the same."

More information can be found in the Watchtower 1984 12/15 pp. 26-29, the article is about 4 pages. But again there are no new Bible scriptures, the Governing Body did not have a dream or vision. They just changed their understanding. These changes often take many years' time from initiating to publication. More information on that can be found in the talk of Mr. David H. Splane (a member of the Governing Body) in the JW Broadcast of August 2016 (timestamp 18:15).