Buddhism started in India. Christianity started in southwest Asia.

Buddhism and Christianity are two of the world's big religions that aren't big in the area where they started.

Christianity was adapted by the Roman Empire and for a while surrounded the Mediterrean, southwest Asia and all.

Then there were intense and nasty fight about what Christians believed, usually about how Jesus did or didn't combined being God and being human.

In these long fights, the people from around the area where Jesus lived lost. The central authorities, to the west of them, in Rome, decided they were wrong. The people who walked where he walked and maybe knew somebody who knew somebody who knew somebody who knew him were more likely to go light on the God part, and say he was more of a guy.

They lost and then, along came Islam. They were ready for a religion that wanted them.