Very few serious and respected scholars doubt the historical reality of Jesus. Few also doubt his crucifixion. What is in doubt is all the other things Jesus is claimed to have said and done. And one of the main reasons for that is that we in the modern age are generally very sceptical of the supernatural.
Secondly, the abundance of literature about Jesus, even if contradictory, serves to prove the historical fact of Jesus rather than disprove it. 1000 years from now people will read a lot of contradictory information about the 9/11 attacks (in even now that is the case). Will the contradictory stories make the fact that it happened less credible?
The fact that at least 29 people wrote their version of Jesus to me appears to prove beyond doubt that Jesus existed.
Secondly what does Jesus writing have to do with us knowing what he said and did? Even today most politicians don't write what they say. In fact, very few people in general write what they say. Most records of what people say are written by journalists after the event. So saying we can't know what Jesus said because he didn't write anything is using a standard so high we would not even be able to believe what people today are reported to have said.