i don't even believe in jesus. as in i don't believe he ever really existed.
so first off i'll define what it means to believe in the existence of jesus: 2 things first the series of events described in the gospels known as the passion, must have, at least in the broad strokes, had to have occurred. and secondly this has to have been the actual origin of christianity. so if there merely was a jewish preacher that was named yeshu that was crucified for some other reason, that's not good enough. he had to have been put to death by the romans conspiring with jews in a factional dispute.
as i see it there are a few reasons that people believe in jesus
they're christians and this goes along with being a christian. although there appears to be at least one notable exception, but i'll get to that later.
they're just going along to get along. it doesn't much matter to them either way but it's easiest to not make waves so why not believe in mortal jesus.
they trust that knowlegeable people have looked at the evidence and concluded that there is good evidence. and this is true, knowlegeable people have come to this conclusion.
that they have actually looked at the evidence and concluded themselves there definitely was a mortal jesus.
the problem is that 4 is weird. i've looked at the evidence and it's a bit hard to understand. not in that the evidence is arcane and i can't understand the evidence but that the evidence is bad and i can't understand the conclusion. it's not convincing at all, it looks like all the knowlegeable people who looked at the evidence and concluded there really was a jesus are all in camp 2, going along to get along. it's stuff like some roman historian mentions jesus's brother when "jesus's brother" must outwardly be just a guy who claims to be jesus's brother. it's only evidence of christianity, not of jesus.
then there is the origin of christianity, it doesn't necessitate a jesus figure to have actually existed. he's a socrates for the pious. a preacher put to death by the state for a pseudo crime he wasn't even guilty of, to which he didn't resist out of contempt or protest of the process. i've heard it argued in response to this that there's no evidence that socrates ever existed, but that of course only strengthens the argument that jesus never really existed. now the notable christian that didn't believe in jesus, that's paul. paul has alot of writings, and conspicuously absent is any evidence of him believing that shortly before then there was a guy who lived, named jesus, who did those things. it's really weird. either it's an outrageous accidental omission, or paul didn't believe in jesus like christians do now.