In your opinion what causes christians to believe in Jesus

[AFTT47]

My bold.

This is something we learned in the early days of the internet. Christians belief has nothing to do with logic, reason, evidence or proof. It's a powerful emotional attachment that absolutely blinds them to the fact that it's Santa Clause for adults. Think of that scene from Monty Python and the Holy Grail where King Arthur battles the Black Knight.

Arthur: "Look you stupid bastard, you've got no arms left!"
Black Knight: "Yes I have!"
Arthur (pointing to his severed limbs on the ground): "Look!!!"
Black Knight: "It's just a flesh wound!"

And so it goes anytime you try to debate a Christian and base your argument on reason or empirical evidence. They just don't care or will refuse to see it.

I believe childhood religious indoctrination by trusted adults and subsequent peer pressure is a significant cause.

Unfortunately, yes. Especially the former. We're extremely malleable as children.