Trho starting a cult is easy and does not necessarily require idiots. All it takes is someone who is a natural leader and is smart enough to know how far to push and in what intervals. You start with something they already believe with a small but plausible twist and then you keep twisting until you get the husbands to willingly offer their wives to you. Once you get enough members the mob mentality kicks in and you can move faster and faster. You get to a point where even the stupidly radical things like declaring yourself the Son of God gets accepted because either they are caught up in the mob, they feel the pressure of the group, or they don't want to think themselves stupid for having believed in you in the first place.

Like evolution. Some geek decided to create a theory that it all started with a big bang to get back at everyone for all the wedgies he got in high school and now he laughs because everyone accepts it on faith.