To be honest, I'm not even convinced that it's a composite figure based on any actual messiah pretenders. Just about everything about Jesus is fulfiling some OT 'prophecy' (read: half-sentence taken out of context) or parallels to the OT or such.
Add some stuff which is clearly symbolic of some attribute of the expected Messiah or of divine power, and some stuff where they're putting in his mouth stuff relevant to their present day (e.g., the anti-pharisee rants and whatnot) and you have Jesus.
Matthew even beats the reader upside the head with what paragraph he's 'fulfiling'. He's inventing a trip to Egypt and back to 'fulfil' some verse from exodus. He's inventing a slaughter of innocents to 'fulfil' something else. He's making Mary a virgin to 'fulfil' a mis-translation to Greek. He's making Jesus ride two donkeys like a circus clown to 'fulfil' another mis-translation. Etc.
Not that the others are better. Mark for example is more skilled but essentially is doing the same thing. You can tell for example that the episode with that physically impossible storm of that magnitude on that little lake in a valley, is Jonah with a twist. Luke seems to include stuff from Josephus too as inspiration.
And not only that, but we're dealing with:
A) a continuation of several sects' tradition to do so as a prophecy of the Messiah, long before there were a Jesus. Seen even in the DSS.
B) a rabidly anti-intellectual new sect (Christianity), which over the next few centuries produced quite a lot of drivel as to why you really don't need to know or study anything else than the Bible, and why philosophy or science are at most good for debating philosophers. I don't think they treated history any better, except for looking for setups for their fiction.
But anyway, once you have the mind-set that what really counts about Jesus are cryptic phrases in the OT foretelling him -- and indeed for Paul it seems to be that the OT is THE source for Jesus and his sect, and if it's said so in the scripture (OT), then Jesus did it -- then you already have the bits and pieces to make a Jesus out of. And again, it's not just something nice to have, to flesh out a character, but from Paul to this day it's
important that he be foretold by the OT. Those are the
important parts. Bits that are just taken from RL characters are not. So once you have that frame of mind, you don't need to borrow anything from any other messianic pretender, when you have a whole big tome of Lego pieces to build a Messiah out of
You could do the same from any book, without needing any data about a real person. E.g., you could take Lovecraft's works and do the same. E.g., my Messiah will be someone who'll be first accepted by the locals, but then the whole town turns on him, because it is 'foretold' so in the plot of The Shadow Over Innsmouth. He'll have a cat for a familiar, for it is said, "
he sat playing with his graceful kitten" in The Cats Of Ulthuar. He'll come from North End, for it is written, "
The place for an artist to live is the North End" in Pickman's Model. He shall descend to the underworld realm of death, for it is foretold so in The Rats In The Walls. He shall be a great scholar, for it is said he "
was widely known as an authority on ancient inscriptions, and had frequently been resorted to by the heads of prominent museums" in our most holy of scriptures, The Call Of Cthulhu. Etc.
I could keep at that long enough and have enough bits to make a Messiah out of without any real person being involved. You just need to be schizophrenic enough -- or force yourself to think like someone with actual delusions of reference -- to find all the material you want in bits and fragments of text about other people, and chip in totally WTH interpretations that the voices in your head... err... the Holy Spirit told you to.
And make no mistake, the fragments I quoted above, are no more out of context or WTH than the ones used by Matthew or by apologists to this day.
Don't get me wrong, maybe there was a Jesus Of Bethlehem, as you call it. Or maybe there wasn't. But far from adding more stuff from other real people, they replaced even whatever might have been known about that one real person with fiction based on the OT and such. His birth, his teachings, his ministry, his deeds, his trials, his execution, and pretty much any other detail have been chucked out and replaced with stuff that 'fulfils' scripture. That's not even making a composite figure out of actual people, but replacing a real person with a fictive Frankenstein-like construct that has as good as no real people parts.