Let me clear up your confusion on early formation of Islam.
Muhammad was born in the year 570.
In the year 610 Muhammad was in a cave outside Mecca when he received his first revelation. Actually, it scared the poop out of him, and he ran to his wife, Khadijah, saying that he feared he was possessed by an evil spirit. His wife sent him to her cousin, Warajah, who was an old learned man in the scriptures. Warajah told Muhammad that he believed he was visited by the angel Gabriel, and that he must be a prophet.
For the next couple years Muhammad kept his call to prophethood to himself and his family. He used to time to study and learn more about the scriptures.
In 613 Muhammad begins to preach publicly about Islam. However he gets few followers. The people in Mecca largely reject his ideas.
In the year 615 Muhammad sends the few followers he has to Abyssinia for their protection. They are only about a dozen followers and they only stay for a year or two.
In the year 622 Muhammad's life is threatened in Mecca and he must flee to Medina for protection. By this time his followers are already in Medina and they have convinced the people there that Muhammad is a wise and trustworthy person. So they appoint Muhammad as an arbitrator between the feuding tribes there.
By 624 Muhammad was raiding caravans from Mecca, saying it was revenge for what the Meccans had done to him. He would only keep 20% for himself giving the rest to his fighters. This was very popular with his fighters, so more people joined him, and enjoying the booty.
Islam would not even exist if (1) Warajah did not tell Muhammad he was visited by Gabriel, (2) his wife and uncle didn't protect him during his early period in Mecca, (3) Muhammad wasn't appointed an arbitrator in Medina, (4) the Meccans battled Muhammad better, or (5) Zaynab, the Jew, was successful in poisoning Muhammad.