When Muhammad declared himself a prophet receiving revelations from Allah, people were joining him for various reasons. Some were attracted by his religious ideas or his personality. They followed him despite the fact that he soon became very unpopular with his clansmen for bashing their gods, their traditions and their forefathers. Some (usually women) just followed their men. When Muhammad emigrated to Medina and started violent jihad, more and more were attracted by the opportunity to rob, rape and enslave, and in general to be the scariest bully in the neighborhood. Some joined him to keep or increase political power. A couple of Bedouin tribes joined Islam because Muhammad was giving out food in the hungry year. But the greatest majority of new converts appeared when Muhammad captured Mecca and destroyed images of pre-Islamic gods, because the tribe leaders understood they were going to be the next target, and chose to join the winner.
So, to sum it up, Muslims of that time had different motivations for joining Islam: religious search, charisma of Muhammad, family bonds, enrichment, political power, fear of violence and persecution, just following the crowd, and of course, various combinations of all the above. And Muslims who engaged in offensive violent jihad were a minority, for very obvious reasons: you had to be male, you had to be of fighting age (say between 15 and 45), you had to be physically fit, you had to own a mount (camel or horse), weapon and armour. By very rough estimate, this makes about 10% of all the community, maybe less.
It often happens that when a cult leader dies, the cult falls apart. When Muhammad died, many tribes decided they had enough and wanted to leave Islam. However, during 23 years of Muhammad’s activity, he raised a group of close companions who became smaller-scale muhammads, thinking like him, speaking like him and acting like him. And they continued with Muhammad’s simple model of success: “Do as I say or else…” The first caliph (leader of all Muslims), Abu Bakr, spent 3 years of his reign fighting apostates and heretics to return them to Islam. Next caliphs, Umar, Uthman and Ali, are known for their further successes in maintaining and spreading Islam by jihad. And since they all followed “Do as I say or else…” model, power struggle was inevitable, and that’s how main division in Islam, Sunni vs Shia, came into existence.
And my main point is the following: right from the start, after 13 years of preaching which brought Muhammad only about 150 followers (roughly one per month), Islam started functioning and spreading as a political system, a society functioning based on Muhammad’s ideas how things should be run, expressed in the Koran and in his sayings and deeds (later collected by his companions in Hadith). Any opposition to this system was ruthlessly suppressed: Muhammad killed, banished or enslaved every man and woman who refused to submit to Islam. Regardless of individual beliefs, feelings and motivations, the rest had to submit or feign submission to the new political system of Islam. And like most people in any society, they just carried on with their personal lives and affairs, not caring much about religion.
And what about the next generation of Muslims, born inside the political system of Islam? They had the same variety of personal motivations and situations making them either more ardent followers or just nominal Muslims paying lip service under pressure of the jihadist minority controlling the system. The only difference is that they were less exposed to alternative ideas or behavior patterns.
Do you think this Islam’s success model established by Muhammad is active nowadays?