In your opinion what causes christians to believe in Jesus

[Sheldon]

The list of conceivable things exceeds the contents of the list of concievable things which are conceivable and coherent, which itself exceeds the list of things that are conceivable, coherent, and actual.  Which is just a whole lot of words to say the very first thing Sheldon said in response to this very question.

All I'm asking him is to explain why he thinks it's conceivable God exists but not possible. 

I have never made either of those claims, I don't believe a deity is possible, I don't believe it is conceivable a deity exists, though I can conceive of one, just as I can conceive of mermaids, or garden fairies, there's a difference between conceiving something, and conceiving that something exists, just as there is an epistemological difference between withholding belief from a claim, and making a contrary claim. One carries a burden of proof, and the other does not. 

 Are these questions really worth drudging over with long repetitive paragraphs, as if your entire intellectual life depended on it? Come on now, you guys are doing too much.

If you had the integrity, to accept the answer, instead of rewording the questions to create straw men, we could have moved on ages ago. 

When will you be giving us your best (or any) reason for your faith a deity exists? You claimed to have many reasons, I asked you for the best one, yet you keep ignoring that question, and repeating the same ones to me over and over and over? Is it a secret or something?

This is pretty simple John, just create a simple syllogism that demonstrates a deity is possible. You can then give us the best reason you claimed to have, for believing a deity exists. though one assumes if you had the latter, the former becomes moot, but since you have refused to offer anything beyond the claim, who can say.

conceivable
adjective
capable of being imagined or grasped mentally.

existence
noun
the fact or state of living or having objective reality.

You see how those things differ fundamentally, and why?