What was common in the religious beliefs of the peoples of the Ancient East? How did they differ?

A common feature of the religious beliefs of the states of the Ancient East was the fact that all large countries and adjacent territories considered themselves as countries whose main belief was Buddhism.
But nevertheless, despite this common religion, in almost all countries, the direction of Buddhism is different.
For example, countries such as China and India and more northern regions belong to the Mahayana branch of Buddhism, and the eastern and southeastern countries belong to the Hinayana branch.
Since the dawn of Buddhism, 18 independent sects have been founded.