re: Dumb question, I know, but is Islam a form of Christianity?

It's 600 years after Christianity starts, traces itself to Ishmael to try to one up Isaac and regards Jesus at best as a teacher preparing the way for Muhammad with Monotheism.

Basically a sand pirate took a little helping here and there combined with his own cultures stuff added his own and due to the incompetence of commands and escorts sent against him people believed God was with him and he rolled with it from that.