Few doubt he existed, and most of those without doubts dwell on numismatic evidence. They didn't even know where his tomb was. It was recently found, but then some issued official expressions of doubt.
They look at things like, oh, Flavius J. and even gospel accounts. But there were other historians.
Palestina was a backwater. It was poor. It was the home of a hated ethnic group that did little but give Rome problems and which, in return for not giving it more problems, had a special dispensation *not* to be forced to give sacrifice to Caesar as god. Even with all that, there were still movements to drive out Rome. The sicarii--which may have roots in 20s and 30s AD, but may have originated a decade or two later--did not produce friends.
Palestina had public works and Roman-built-and-planned cities--Capernaum, for instance--but those were for wealthier Jews and for Romans (or at least non-Jews).
As for texts being important things, more than a few researchers suspect that various gospel accounts go back to lists of sayings of Jesus that *were* extant as early as 60 AD and must be older. It's unclear that Paul saw or had any, but that's an argument from silence. They were rendered unnecessary when the edited compendia came out. (In this, it rather resembles the lists of Muhammed texts that Uthman allegedly pulled together to make the Qur'an--if he even was the one to pull it together; note that the lists themselves don't survive for all their awesome awesomeness. It's also worth noting that the first accounts of Muhammad's life date to a century or so after his death, and the time depth of Jesus versus Muhammed's accounts would be about 2000 versus 1400 years.) For all the record keeping, there's no contemporaneous mention of Muhammed or of his mighty military campaigns. (And one can make the argument that if Muhammed existed, he borrowed a lot from pre-existing sources, and that might have been because he saw scattered tribes confronted with two more prosperous or politically better connected groups, Jews and ar-Ruum, both united by a book with a strong prophet at the center of each, each group united by their book and prophet. I mean, how humiliating is *that* comparison? Ahem.)
Not only was Jerusalem destroyed and the territory of Palestina pretty much laid waste during the period when Xianity was still mostly a Jewish "thang", but even then the Xians that were there weren't much appreciated. They may have hung out in the synagogues and done the mandatory rituals, but I doubt that the synagogue leaders were highly appreciative. Note that the Academy set up at Jaffa undoubtedly had a lot of writings, but all that remains are the Tosefta and Mishnah, with the Palestinian Talmud's underlying sources largely gone, Temple and synagogue records erased from history. There were more scrolls and writings than just those, to be sure, but that's it for the strain of Judaism that became Rabbinic Judaism. As for other sects, the Sadducees and the Essenes (etc.), they're gone. It wasn't until the scrolls at Qumran were found that they were known from anything more than a general reference in Flavius J. (and even now the identification is sort of by default, not because of a scroll that said, "We, the Essenes, believe ...) Making it harder, within a century or two the dominant strain of Xianity was gentile and the roots shifted from Torah-observant to pre-Catholic/Orthodox, and the original bearers of the Jesus-sayings lists would have been considered old-school heretical.
The earliest bits of the OT were in Greek from the 2nd century BCE. Want more, until the Qumran texts you'd have to look years after the destruction of Jerusalem. The Old Syriac is older than the earliest most Hebrew texts. Yet there's as much textual evidence for the Tanakh from 560 BCE or so as there is for the Qur'an before the early-mid 700s, and given other finds it's likely that at least portions are hundreds of years earlier. The textual history of the NT is similar--first bits are early 2nd century, but it's still likely Paul's epistles really are mostly Paul's, and before 70 AD.
In other words, your conclusion's like the filling in a Czech buchta: You bite into and are surprised discover it, even though it was baked into the bun by the baker.
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