Well when Joseph SMith came out with this new book, a lot of people believed him, and a lot still do, so there must have been something he did to make people believe him. People simply do not just follow blindly, especially not multitudes of people.
Stereotypically, people i know and myself have always thought of the mormans as the crazy christains who ride round on bikes trying to convert, but they're no different to any other religion in any way other than age. The word of god is the word of god, regardless of when it was written. Since no evidence of god exists all people have is faith, and thats all that counts for some, just because a religion is older doesn't mean it is more holy, or better.