What did Buddhism vs. Hinduism mean politically?

The Caste System is philosophically/politically/culturally unacceptable to the Chinese based east asian civilizations.

So when the Chinese imported Hinduism / Buddhism from India, all the stuff (The caste system, most of the hindu gods, and virtually all the myths) that didn't appeal to their sensibility were left behind.

My understanding is, only the philosophical concepts were taken.

And the political impact is hard to overstate.

even for the ruling class, the caste system is a double edge sword. While it made the populous much easier to control, it also disenfranchised 80% of the people. What do the people of the bottom 2 castes and the untouchable care about the fate of the ruling class? It isn't their country. This I think is why India has historically been a surprisingly easy subcontinent to conquer.

And the Caste System's rejection of social mobility also created a culture of illiteracy and apathy among the lower classes that persists to this day, keeping India down as a country.

Lord Buddha was a Kshatriya- though if he had wanted to be a Brahmin he could easily have received into the priesthood of one or other of the leading lineages. However, in that case, he'd have been expected to get married and have sons. He preferred the life of the Shraman- renouncer- who has gone beyond caste and family.

This did not mean Buddhism abolished Caste or Untouchability- it helped spread it as far as Japan where there are untouchables but no Brahmins whereas in Bali there are Brahmins and Kshatriyas etc. but no untouchables

Judaism came to South India a few centuries before Christ while Christianity and Islam appeared almost immediately after their inception. They all have Caste and mistreat untouchables. Arundhati Roy and Sujatha Gidla are famous Christian authors who have exposed this. The Chief Rabbis of Israel did tell the Indian Jews to get rid of Caste in the Nineteen Thirties- at about the time Hinduism was reforming itself in this regard. However, it was only in Europe where Indians of an untouchable case- the Doms or Romanis- were subjected to genocide by Hitler.

The main limitation of Hinduism was that it was a "local" religion, to the Indian subcontinent. The term Hindu derives from "Sindu," a part of India. Over the two hundred years or so after 500 BCE, it was formed by a "fusion" of various Indian traditions. It may be considered the Indian version of China's Confucianism, oriented toward ethics, rituals, and astrology, where the role of deities was implied, rather than explicit.

Bhuddism was a "takeoff" on the antecedents of Hindu religion that did not develop contemporaneously into the Hindu mainstream, even though it shared important concepts such as "Dharma" with Hinduism. Bhudda preached "Four Noble Truths" about 1) a cycle of 2) suffering 3) death, and 4) rebirth. An important solution to life's problems was reincarnation, and steadily improving reincarnations could lead to Nirvana, or perfection. Put another way, one's current life was only one of a series of "iterations" (in modern technical language), and doing one's best in the current life would lead to a better future incarnation. This was a philosophy that had "universal" appeal (that is, in many parts of Asia, outside of India).That may be why a Japanese emperor adopted it. Even so, Bhuddism stood the caste system on its head by promising people that good behavior in the current life could lead to birth in a higher caste in the next reincarnation, while one's current low caste was because of misbehavior in a previous life.

600 B.C. was roughly the beginning of the Mahajanapadas (Great States). It saw the beginning of not only small kingdoms, but also major urban centers. The era is marked by the transition from Painted Greyware to Northern Black Polished Ware. NBPW was a luxury item used by the new urban elites. Parallel with the growth of cities was a major increase in long distance and foreign commerce. All of these things led to a new economic and political situation which the Brahmans could not maintain control. Ideologically, Brahmanism failed to capture the minds of the new Urban class. It had come to include dozens of archaic gods. To become a Brahman, one had to memorize the entire Vedas. These grew in size, and the memorization become more and more tiresome.

In the 6th century B.C., Amidst these social and political upheavals, the Sramanas appeared in Maghada, and neighboring Videha. These were philosophical movements professing a simpler doctrine of aestheticism and liberation. The adherents of these ideologies were naked mendicant-yogis who lived in the woods. Alain Danielou, who lived and studied in India, said that these Yogis were preservers of an indigenous Harrapan tradition which had moved underground when the Aryans arrived. Indeed, one of the meditations of the Shivaites was to feign madness, by which they would avoid persecution and be left alone. Many of them were darker skinned Dravidian types. Their wisdom attracted the ears of the new urban class.

The revolution was very much commercial. The adherents to Buddhism, a Sramana movement, were Brahmans who were successful merchants. Hinduism wasn't accommodating to the needs of merchants. After all, merchants were the second lowest of the four classes. It didn't guarantee their safety, or the unimpeded movement of goods. Their ability to do business was at the whim the local Brahman priests. Buddhism, with its universal clause of non violence, allowed for the unhindered flow of commerce, which translated to wealth. Kingdoms had a vested interest the flow of commerce. Politically, Buddhism had another caveat. The burgeoning amount of hindu gods had the effect of chaos and disarray. The simple, unified message of dharma helped create political uniformity. This was definitely the motive for Ashoka's conversion. He incorporated these political and economic elements into his ideology of "peaceful conquest".

Hinduism was ultimately adaptable to less archaic governments and economies. It just so happened that Buddhism filled a particular niche when it opened up. By the present era, Vishnavism and Shivaism were created, which also served as a counterweight to Brahmanism. Vishnavism, for instance was popular with foreign merchants in the ports, who probably would have earlier been Buddhist. Buddhism appeared more like Hinduism after the creation of Mahayana Buddhism.

Alternately, I recommend reading Tornada's blog about the point of view of the authors of the Mahabharata. It explains how they viewed the expansion of Maghada from a Hindu perspective, decrying the violations of sacred Kshatriya-kings rights. It's shows how the two world views clashed, and ultimately Buddhism prevailed.