Why are there so many Muslims? Simple question.
My guess as to why there are so many Muslims in the world is that Mohammed wanting to be unto God but could not be another like Jesus Christ by way of Sahra/Joseph/ David started his own path to his Allah in the world not dominated by Christians. His world was heavily populated.
It’s an ideology that empowers the poor and envious and punishes everyone else, the royal house of Saud, not withstanding. It’s appeal in our prison system to, IMHO, self-pitying-disenfranchising folks is a good case. The “West” is a success, and that leaves the rest wanting and angry. Allah empowers that rage.b