The idea of Jesus as a complete fiction is much more problematic, because then one has to explain why all of a sudden a series of texts in the first century were devoted to a single person, placed him in a specific context, and treated him as a historical figure. This isn't true for other cultic figures like hercules or osiris. It isn't just that the myths surrounding these figures place them in a far distant past, it's that they are far more highly variable and spread out in time. They don't just simply appear.
If, however, he was a charismatic healer/teacher/leader who inspired a relatively small following among a highly illiterate subgroup of a culture already under domination by another culture to which most of the historians belonged, we would be suprised indeed if any mention of the man was recorded within a century of his life. Which is why we are extraordinarily lucky to have epistles, bioi, and a few references from several different historians all within a century, some by contemporaries or near-contemporaries.
On what do you base this statement? Paul was more influential in many ways, in that as a missionary he travelled farther and converted more, and was interacting with both pagan and jewish cultures, and yet he isn't mentioned by anyone outside of christian circles. John the baptist was influential enough to be in the NT and Josephus, but isn't mentioned by anyone else. The teacher of righteousness is unheard of outside of the qumran documents. Apollonius of Tyana was a miracle-woker, but he isn't mentioned more than in passing until a century after his death. Why on earth do you think "historians" would have written about a relatively obscure prophet/teacher from galilee who gathered a following? Oh wait. Because
The Jesus Mysterties said so.