If I was not a Muslim I will be still amazed how a single man in Arab desert has 1.3 billion followers even after 1426 years.
1- He was one and Muslims over a billion.
2- He did not read or write and most Muslim scientists are faithful believers.
3- He came from a violent culture and created a peaceful religion unless attacked.
4- He came from hard headed Arabs and gathered all Muslims in one heart despite all of their differences. Without Islam very likely they would be more violent with lower morality and spirituality.
5- He came from a pagan materialistic culture to a highly spiritual religion.
6- He came from fighting tribes to create one community that almost functioned as one democratic government.
7- He came From intolerant society that measure people with their possessions and origin to a righteous society judge people by their morals.
8- He came from less civilized tribes to create the greatest civilization the world knew.
9- He had his enemies became his friends and the army leaders of his enemies became his army leaders.
10- He came with a religion that broke all the walls of ethnicity, color, region and materialism to the simple basics of humanity and morals.
11- He made faith as it should be built first on reason (mental belief) and then feeling spiritual belief).
12- He made faith to go both ways a positive confirmed belief and for the very skeptical a default believe when it becomes very difficult to disprove the Quran and its reasoning.