Religion

And even there, we are not 100% certain he existed.

Compare it to the evidence for an historical Thales of Miletus and it isn't too different from Jesus. We have no contemporary records of Thales. The records we do have were all written later and conflict with each other. So it's possible he didn't exist. Some have argued that.

If that's not good enough, there are plenty of other ancient people about whom we know almost nothing, just one or a few references to such a person. There are stories of wonder working rabbis in the Talmud. We think the rabbis probably did exist, but the works of wonder are just stories, like so many other ancient stories. You can say none of them ever existed, but there are 1,500 rabbis mentioned in the Talmud, so it seems strange to make up a huge number of nonexistent people to disagree with each other in your authoritative law book.

We think Sargon of Akkad existed, but there are no contemporary records and we have never found the City of Akkad. Sargon's name is found in king lists that were all written later and contain obvious fabrications. We have stories about Sargon that are likely fabrications.

You can dispute the existence of lots of ancient people if you want. Some people make an academic career out of disputing some historical fact or of proving an historical fancy. You can do it as a dodge or just to get tenure. Which I am not doing, so I don't even see why that's relevant. I'm just taking my best guess.