The history of Christianity is loaded high with forced conversions, from the use of Constantine's declaration against the pagan world right through to Charlemagne's campaigns against his neighbors in northern and western Europe. It was a routine feature of the European colonization of both Americas and Africa, and with African slaves brought to the US, Caribbean and elsewhere.
Not at all strange once you acquaint yourself with the problems of the NT documents from an historical rather than a believer's point of view.
There's no need for Jesus to have existed in history to have influence as a religious idea. Gautama Buddha was likely a real person, though which of the suttas attributed to him are his is an ongoing debate. It seems more likely than not that Muhammad existed in history, but none of the sayings attributed to him in the Qur'an can be shown to be his and very likely are not. But it doesn't matter ─ the religions led by Brahma, Osiris, Zeus, the Great Spirit, the Rainbow Serpent and so on have all been very influential in their cultural spheres at their relevant times.
Then why do you think humans have to be 'redeemed' at all? Redeemed from what, exactly? Redeemed by what process, exactly? I find the concept singularly empty as a statement about reality.
None of them did. Mark devises the only purported biography of Jesus by stitching bits of the Tanakh together which the author takes to be messianic prophecy, the author of Matthew copies it but rewrites the parts he doesn't like and adds some 'fulfillment of prophecy' tales of his own, the author of Luke copies Mark, corrects them both and adds some tales, and the author of John presents a fifth version of Jesus.
If there's any sign of a real human in any of that, it may be that an historical Jesus was conceived out of wedlock, fought with his family and never had a kind word for his mother; and had some physical defect which would lead to his 'physician, heal thyself' line. His message may have been, Get ready, the Kingdom is at hand. Paul says his name wasn't Jesus until after he'd been crucified. Or maybe there was a real Jesus but none of that is correct. Or maybe there was no real Jesus.
As I said, none of the gospel authors claims to be an eyewitness, and the texts confirm this. And John wasn't written till some 70 years after the traditional death of Jesus.