OK then let me be the first to reply that it's POSSIBLE that the Jesus belief started from not-a-man. But that it's the problem here. The problem is that, assuming we want to reach a conclusion at all ("I don't know" is perfectly acceptable), which of the alternatives is more probable ? Dejudge likes to remind us that I said the evidence is terrible. How about MJ with its zero evidence ?
As I have pointed out before (with cited examples) not all MJ theories are the same.
There is John Robertson's 1900 "The myth theory is not concerned to deny such a possibility (that the Gospels Jesus is partly based on a real person). What the myth theory denies is that Christianity can be traced to a personal founder
who taught as reported in the Gospels and was put to death in the circumstances there recorded." Wells current theory fits into this form of Christ Myth theory and has been called such by Stanton, Eddy-Boyd, Carrier, and Price.
There is Remsburg's historical myth in "the narrative is essentially false" vein ie "the story of Jesus is a piece of mythology, possessing no more substantial claims to historical fact than the old Greek or Norse stories of gods and heroes..." reiterated in 1982 and 1995 by the HJ side of the fence.
There is Price's "the central figure of the gospels is not based on any historical individual", i.e. the
Gospel Jesus is little more than "a synthetic construct of theologians, a symbolic 'Uncle Sam' figure." which is essence the "HJ" the Jesus Seminar gave us.
There is Herbert George Wood's 1934 "theories that regard Jesus as an historical but insignificant figure."
And finally per Schweitzer in 1912 and again in 1931 Sir James George Frazer.
As for evidence for the more moderate MJ theories there is plenty of evidence:
1) The Euhemeristic mind set of the day is well documented. Eusebius in the 4th century CE accepted Heracles as a flesh and blood man who by birth was an Egyptian and was a king in Argos.
All myth was distorted history to these people. "Osiris, Attis, Adonis were men. They died as men; they rose as gods." was basically the mind set of the day. No one of that time or even three centuries later would question Jesus existing as a person because they believed that Heracles and Zeus had once been flesh and blood people.
2) As documented in Carrier's
Kooks and Quacks of the Roman Empire: A Look into the World of the Gospels you had a ridiculously gullible, credulous, superstitious group of people willing to believe any story that came down the pipe and willing to declare people "gods" for things as simply surviving snake bite.
3) We know from Josephus and others that the place and time was teaming with not only "cheats and deceivers claiming divine inspiration" but totally delusional nutcases who led their followers to destruction. Visions were sometime regarded as powerful messages from the "gods" so Paul would have not too hard of a time with a exists only in visions Jesus.
4) No of the details regarding the trials, behavior of the Romans, treatment of the body, etc in the Gospels or Acts matches what we know about them from other sources...suggesting these accounts are fictional.
5) We know from John Frum and other cargo cults that not only does a religious movement not need a founder but the cult may latch on to a person who has nothing to do with the cult's founding.
6) The best argument the HJ side seems to have is minimize Jesus actual presence to just above nil...which when you think about is saying he might as well not existed because the majority of the Gospel account is fiction. To quote Carl Sagan here "why not save a step" and throw the whole thing out?
7) Per Eddy-Boyd I don't know
is a MJ position.