Until someone comes up with a plausible explanation for a no-Jesus scenario, the idea that the stories were based on a human being is the winner of any plausibility contest.
I know Richard Carrier is working on something, but he hasn't convinced me yet.
But as I have repeatedly pointed out there
already is a plausible explanation for a no-Jesus scenario: the cargo cult to John Frum model.
"
Unlike the cult of Jesus, the origins of which are not reliably attested, we can see the whole course of events laid out before our eyes (and even here, as we shall see, some details are now lost). It is fascinating to guess that the cult of Christianity almost certainly began in very much the same way, and spread initially at the same high speed." (
Dawkins The God Delusion chapter 5)
"
In particular, they suggest four lessons about the origin of religions generally, and I'll set them out briefly here. First is the amazing speed with which a cult can spring up. Second is the speed with which the origination process covers its tracks.
John Frum, if he existed at all, did so within living memory. Yet, even for so recent a possibility, it is not certain whether he lived at all. The third lesson springs from the independent emergence of similar cults on different islands. The systematic study of these similarities can tell us something about human psychology and its susceptibility to religion. Fourth, the cargo cults are similar, not just to each other but to older religions.
Christianity and other ancient religions that have spread worldwide presumably began as local cults like that of John Frum." (
Dawkins The God Delusion chapter 5)
So the basic no-Jesus scenario is:
1) a "Christ" cult forms c100 BC out of the story of the Teacher of Righteousness. It doesn't attract too much attention as the membership is small and the members are relatively quiet.
2) Several people try to be this "Christ" all of whom are dismal failures.
3) Several "Christ" cults hear the name "Jesus" and proclaim him as their founder. What "Jesus" actually taught or if he even existed doesn't matter to them.
3) Paul persecutes several of these "Jesus" Christ cults and then has his vision. Through his teachings pushes one particular version of the "Jesus" "Christ" cult denouncing all others in 2 Corinthians 11:4.
4) Mark (70-85 CE) is written and becomes so popular that it become the to go to work for the life of "Jesus".
5) Marcian collects all the then known letters of Paul and adds one of the derivatives of Mark, "Luke" to his work creating the first Christian bible (c140). It goes over like a lead balloon but gets many of the cults to go and try their hand at hammering out a bible of their own.
6) The Paul "Christ" cult hammers out its definitive canon by c180 and due to its spread is the version of Christianity adopted by the Empire leaving all other to either be persecuted or drift off into obscurity.