Why appoint Matthias to replace Judas only to later appoint Paul as a thirteenth Apostle?

Matthias was mans at attempt to complete the prophesy and bring the number back to twelve. The 11 were not asked to do it nor did they ask God if they should. They only assumed they should. They chose between Him and another by lots. Notice Matthias never did anything. Paul was chosen by Jesus as the other 11 were. Paul is the true 12Th. notice Rev says there are 12 names on the wall? We know one of them is NOT Judas. and if you add matthias that's 13. What ever you conclude, it can't be a contradiction.

Jesus is referred to as an Apostle in Heb. 3:1–2;

1 Wherefore, holy brethren, partakers of the heavenly calling, consider the Apostle and High Priest of our profession, Christ Jesus;

2 Who was faithful to him that appointed him, as also Moses was faithful in all his house.

This is a designation meaning that He is the personal and select representative of the Father. It also makes him a thirteenth apostle in addition to the twelve, but with a different role than the twelve.

Christ conferred the keys of the Kingdom of Heaven unto Peter. If this made Peter the successive representative of the Father on earth, then that would have left two open positions in the quorum of twelve apostles, not just the one left by Judas. Matthias was called to fill the position of Judas, Paul may have been called to fill the open position left by Peter, who was advanced to assume Christs position as High Priest of the church.

I had no idea that upon questioning the number thirteen I would find an Old Testament pattern that does seem to reappear in the New Testament. However I have not found this seeming perfect match made notice of by my favorite Bible commentators so I remain in doubt whether this is truly prophetic or just a very convenient coincidence.

In any case it does answer the question, at least making one not be so fussy about twelve, verses thirteen. The fact is the tribes of Israel started out as 12 but then a double portion went to Joseph, so two of his son's (Manasseh and Ephraim) became their own tribes. Technically the tribes of Israel started at twelve and then became thirteen.

Furthermore, when Jacob blessed the two sons Manasseh, the first born was to have the greater blessing, but Jacob reversed the order saying:

Nevertheless, his younger brother shall be greater than he, and his offspring shall become a multitude of nations. (Genesis 48:19)

Actually, Ephraim became so prominent that it came to designate the northern kingdom and Judah denoted the southern kingdom.

It seems that in some ways then the loss of the one office which needed replacement was possibly resurrected into an unpredicted double portion when the youngest, Paul, became the office that was greater greater, even as 'a multitude of nations' being brought into the blessings of the gospel. This large blessing to Ephraim, which Messiah was not to have his lineage from, may act as a symbol of the Gentiles being a thirteenth tribe included in the twelve. Under this view Matthias corresponds to Manasseh filling out the Jewish offices and Ephraim to Paul indicating the ministry focused on Gentiles. Literally 'the odd man out' at thirteen, yet became greater than the other which completed the twelve.

Symbolically as the original number was twelve, twelve remains the figurative symbol for all the tribes and apostles.

One has to admit the coincidences are more than singular in the convenient parallels. Yet it still begs the question why would Paul, not mention this? Possibly he did not notice it for it was God's blessing on him for always considering himself the least. In support of the theory, when we read the book of Acts, Paul really is the trail blazer.

The wall of the city had twelve foundations, and on them were the names of the twelve apostles of the Lamb.

Revelation 21:14 (emphasis mine)

At issue here is who the 'apostles' were, and how many there were. See this question, "How many apostles are there". Or this one, "Who was the 12th apostle...".

The underlying premise is in question. Scripture lists upwards of the possibility of 25 people as apostles. Peter, in Acts 1:20, says the reason for the election of Matthais, quoting Psalm 109:8, "Let another take his place of leadership".

From the passage in Revelation, while there are numerous people mentioned as apostles, there is a distinction between the "apostles of the Lamb", the twelve, and those who are called Apostles after that.

While some would disagree, I believe, with respect to Revelation 21:14, that Matthais's name, not Paul's, will be on one foundation, as he was specifically elected (by God, through men), to fill that vacancy.

Paul, too, is an apostle, not less than the "super apostles", also "least of the saints", and "chief of sinners". But, simply because Scirpture records largely the activities of Paul, and not others, does not mean that they weren't very fruitful.

Matthias was appointed for a very specific purpose: to fill the void in the Twelve once Judas had died. We have no record of when or under what circumstances Paul was called as an apostle, but we do know that his ministry coincided with a period of very heavy persecution for the church. So it's not at all unreasonable to assume, in the absence of any evidence to the contrary, that Paul was appointed, as Matthias was, once one of the other existing apostles was killed.