Most likely alternate major world religions?

God damn it, I double posted by accident but for some reason both my posts got deleted.
So abridged...

Initial Byzantine response to Islam was to view it as simply another Christian sect. Muhammad himself did not believe he was founding a new religion. He believed he was simply continuing the same faith as Abraham, and all the other prophets before, including Moses and Jesus.

The idea of "Islam" and "Muslims" is a later invention. That term wasn't even used at the time. They simply called themselves Muminin - "believers".
Yeah no.
Muminin is a general term for followers of monotheism, so whilst Muslims might describe themselves as such (and indeed the Quran does call them that), the Quran also not only distinguishes Muslim from Muminin, but the same section in which it does tells Muslims to tell non-muslim muminin (a tongue twister o_O) that the muslims profess Islam and that the true faith has not yet reached their hearts.

So the only thing that early islam held in common with what you describe in the post is that technically Abraham did beleive that he was continuing the faith of Abraham, but beleived that Christianity and Judaism had diverged enough to the point of being different religions.
Have Genghis Khan impose Tengrinism on his subjects instead of being pro religious freedom.
That is a good way to abort a mongol empire rather than boost Tengriisms numbers.
That multiculturalism was one of the reasons that the mongols were able to expand and absorb conquered steppes tribes into their empire so quickly. Remove that and you are going to have a major problem with a good chunk of his military.
 
I'm genuinely curious as to what the world would think of classical Greek paganism if it didn't go extinct.

There's a remote chance that via ERE screw and Bosporan Kingdom wank you could keep a community of Greek pagans around in Crimea into the 2nd millennium, maybe even until the alt-Renaissance happens, which would interest many of the writers of the time. No doubt they'd find a rather Christianised, very peasant form of the Hellenic faith with many local influences from Scythian to Turkic rather disappointing compared to the religion which inspired the writers of Antiquity and had huge temples built in its name.
 
Top