Well, if Mohammed pulled it off, why not Temujin?
Because Mohammed was an urbanite and Temujin was a pastoralist.
The end.
Well, if Mohammed pulled it off, why not Temujin?
I think that to become a evangelistic religion, Tengriism needs a Holy Book, or books. But the written Mongol alphabet only developed after a Uighur scribe was captured in 1204. This doesn't leave much time for the development of a written body of religious material, but then that might not take too long to accumulate.
Also, Islam managed to succeed so well at conquest because it ideologically gave the Arabs a basis for accepting and tolerating other peoples. Yeah, that sounds paradoxical, but Islam meant that Arabs (1) had to care about the fate of the soul of other peoples and (2) had to accept that Christianity and so on was OK, which made conquest much easier.
I don't see a whole lot in the Mongol character that parallels this.
the Mongols retained a measure of centralized government, while the Muslims were only united as far as religion and culture, but became more politically divergent the further they spread out.
What if if Gengis Khan, or an ATL analagous, not only unites the Mongols and leads them to war against their neighbours... but also creates a monotheistic religion. I know that seems too much for a single person, but I don't see why something like this couldn't have happened.
This religion could be a mix of Buddhist, Nestorian, Islamic and Pagan elements. It would be a Mongolian Faith at first, but it may accept non Mongol converts later.
Could such a religion gain converts in areas were other Monotheistic religion had existed for centuries? If so, only if conquered by Mongol armies? How would the world differ from our own in such a TL?
In this sentence I think you are getting the two civilizations confused. The Arab Empire (Rashidun, Umayyad, and early Abbasid) was centralized and united for longer than the Mongol Empire.
Although seeing as the Mongols were absorbed within a generation or so, that "national unity" did not seem to do them much good.So, like...Genghis pulls a Muhammad?
Could work. Just modify Tengriism into a truly monotheistic faith that proclaimed Genghis's line as the sole legitimate line of rulers for the world.
Though it might hamper the Mongol Empire's OTL long term success. One of the big things that helped the Mongols was that they had an overarching sense of national unity, that put religion second to be part of the horde.