Muhammad is remarkable amongst legendary religious founders, in that he is at once supposed to have been a regionally significant secular figure who somehow left no mark amongst his contemporaries of his existence.
On balance, I’m inclined to believe that a man named Muhammad did exist, but that his secular role was embroidered over time and that he was presented post-facto as the leader of the Arab conquest when he was more likely just its most “spiritual” capo who provided the theological justification for the “bandit socialism” the Quraysh and their allied tribes were imposing on the region.
That Muhammad, according to tradition, made no clear arrangements either for a successor or even for the process by which a successor should be chosen indicates strongly that Muhammad’s secular role in the community, if any, was exaggerated.
The whole Shi’ite/Sunni struggle is a central indication of the historical sand upon which much Muslim tradition is built.