In OTL, a monotheist religion emerged among the Arabs at just the right time, and in just the right place, to unify the Arabs and spread itself through military might across Arabia, North Africa, Persia, Anatolia, Central Asia and so forth, the become the world's second largest religion today. I'm talking about Islam of course.
But what if that persuasive Prophet had been born in another nomadic desert society, among the Tuareg of the Sahara? What if some enlightened trader among the Tuareg, having travelled among the Christians and the Jews in the North, and conversed with the animists and pagans, created his own faith?
Could this have caught on among the Tuareg confederations, allowing them to unify and spread the faith through military might to the Africans in the south? During a turbulent period, might they have swept in from the desert and conquered North Africa, Egypt, and into the Levant, bringing them all into the true faith?
Just a thought.