Obviously Jesus the man existed.
But even if he had not existed, it is obvious that the pharisees
(rabbis) were friggen crazy, generally hateful and vicious, were making,
like modern social justice warriors, a power grab through claims of
superior holiness, trying to out holy the traditional hereditary
priesthood, and leading their people to self destruction, thus
inevitably someone claiming to be a prophet of God would have arisen to
call them out, and would have been executed for his troubles.
Also inevitable that that prophet, if not of the line of Aaron, would
claim to be of the line of David.
The self destructiveness of today's Jews is a faint echo of the
destructiveness and self destructiveness of the rabbis at that time, who
got them enslaved and exiled, and their endless legalistic
interpretation and re-interpretation and re-re-interpretation of the
Jewish law is what got them into trouble in the first place. If Jews
had stuck with the hereditary priesthood ordained by Moses, they would
not have gotten into all this trouble, nor caused all the trouble that
they have caused for other peoples.
The Rabbis got their people killed, and those that were not killed were
enslaved and/or exiled, but the rabbis got what they really wanted.
They got power and the hereditary priesthood lost power, at the cost of
destroying Jerusalem.
So of course a prophet must have existed complaining about this crap,
and of course his life and words would have somewhat resembled the life
attributed to Jesus, in that he would criticize the hypocrisy and
legalism of the religious establishment, in particular and especially
the hypocrisy and legalism of the pharisees, and would have died of it.