They were like snowboarders and skiers, or like the Westboro Baptist Church and everyone else. At its core, Islam is what we call a radical reforming religion. Just as Jesus and Moses sought to restore Abrahamic monotheism after what they perceived as straying, so too did Muhammad. Muslims believe that God sent Muhammad as the final prophet to bring people back to the one true religion, which involves the worship of and submission to a single and all-powerful god. The Quran also acknowledges Abraham and Moses and Jesus, among others, as prophets, but it's very different from the Hebrew and Christian Bibles. For one thing, it's much less narrative, but also it's the written record of the revelations Muhammad received, which means it's not written from the point of view of people. It is seen as the actual word of God.