What do actual, existing persons do that makes a legacy that can be verified?
Art, music, literature, poetry, military conquest, monuments, wisdom teachings, etc.
Is the Jesus represented by scripture identifiable by any of the above? Did he himself produce any of those things with his own hands?
Instead, we have a jew functioning under an existing system who is an ethical critic. He (if he existed at all) must have had charisma and authority when he spoke. But, as in all things human, he was heard differently by each listener who, then, went on to speculate and expand on the "meaning" of what they perceived.
This can happen to anybody. What they are becomes something more than what it really was.
Take Elvis, for example.
Elvis died and he has been seen here and there by fans (even though he couldn't be where they saw him.) But, we can prove Elvis existed by photos, newsreels, recordings and perhaps our own eyewitness accounts. If we had ONLY the eyewitness accounts to go on we'd lump the Elvis sightings in with the actual eyewitness accounts and discover that Elvis was alive AFTER HE DIED! Then, we might have to rethink what sort of man could do that. This would lead to another and another rethink about the meaning of Elvis' music and his messege, etc. etc.
So too with Jesus.
For Jesus to be an actual person (much less a god-man) he'd have to impact history with some actual creative handiwork. Jesus did nothing. Nothing. Nothing at all. Those who make CLAIMS on behalf of their representation of Jesus are the ones who impacted history for real. We are dealing with their Jesus just as we deal with Mickey Mouse as the representation of Walt Disney's imagination and animation and studio productions. A legacy for a mouse. There was an actual mouse, to be sure, but--you cannot expect any realistic knowledge about Disney's actual mouse by watching Mickey Mouse animation.
So too with Jesus.