Why do Christians become Christians?

[Brian37]

Buddhism got started as a rejection of the Hinduism it was spawned from.

You do realise that Buddhism is at least 100 years older than Hinduism? They both come from similar base traditions, but while Buddhism was in all likelihood a unified religion from the start (c600BCE), Hinduism was a synthesis of different traditions and religions, likely starting at around 400BCE and not finalised into anything like its current form until 500CE.

I think that depends on which sect of either you ask. But their shared history still existed in the same area and the overlap is obvious. The evidence shows that they arose from the same ideas.

Brahmaism is older than Buddhism.

https://en.wikipedia.org/wiki/Brahma It says that the first depictions were Vedic in nature and 1,000 years BCE.

 One of the earliest mention of Brahma with Vishnu and Shiva is in the fifth Prapathaka (lesson) of the Maitrayaniya Upanishad, probably composed in late 1st millennium BCE. Brahma is discussed in verse 5,1 also called the Kutsayana Hymn first, and expounded in verse 5,2.[20][21]   

That's older than both the numbers you gave.



https://en.wikipedia.org/wiki/Buddhism_and_Hinduism