Jay Smith on Islam

His thesis is something like as follows:
1. Islam started as a heretical Arian-like Christian sect.
2. The Koran was not compiled until ~150 years later to create a backstory and was cobbled together from Christian and Jewish texts written in Aramaic. Mistranslations explain the baffling parts of the Koran.
3. It follows that Muhammad never existed. References to the name, which means "the praised one" originally referred to Jesus. Similarly the city of Mecca didn't exist in the seventh century. The great city referred to was most likely Petra.

Interesting stuff. If true it appears that Christianity is the only real Abrahamic religion.

Early Islam was successful and won battles against two empires with great odds stacked against them. Their success means at least they are on to something

Yes, Arian Christianity seemed to hold great appeal to certain societies such as the Arabs and Germans.