People cause Religion.

is a secular view.

No, it's pretty much the only view. People did create religions. Unless you are suggesting an alien race created religion then erased out our memories to the matter.

Who created Christianity?

I don't think there is a direct answer to something so huge. Paul is credited with creating a lot of Christian theology and could be seen as the human 'creator' of many of it's aspects in a sense, then of course Jesus could be seen as the 'spiritual' creator and the poster boy that keeps it all together.