User blog comment:LurkerLordB/Religion in a world without Christianity/@comment-3218619-20120424222609

Also, "Allah" and really Islam came from one of the dominant gods at that time, the moon god. This was all before Islam came into existence. He was worshiped by the Sabeans, and his symbol was the crescent moon.

So, Muhammed copied this "Allah", and his symbol, the crescent moon. Notice how the crescent moon appears in almost all aspects of Islam, with even Ramadan's beginning and end symbolized by the crescent moon.

Muhammed wanted his own religion, but if he tried to start one, he was afraid it would be viciously beat down by the other major religions of the time. Therefore, he took Allah so he had a large population base to convert, and so he had a large tribe to back him up.

So, Allah and Islam really wasn't based off of Christianity, it was based off the Pagan religions of the time. Therefore, even if Christianity didn't exist, Islam would exist, albeit in a changed form. Islam really was from Judaism, not Christianity. The split is when Abraham sacrificed his sons, Muslims believe that he sacrificed Ishmael, instead of Isaac.