The forerunners of the FLDS broke away from the mainstream LDS church around 1890, when the mainstream church publicly disavowed polygamy. Since then, polygamous Mormons have splintered into a large number of individual sects. The leaders of these sects all claim that they are the rightful successors of Joseph Smith, and that their sects are the one true Mormon church. The FLDS church is one of bigger splinter sects.
That is the root of the problem. They are following Joseph Smith. Every blasted one of them.
Not God.
Not Jesus.
Joseph Smith.
And when you follow man, you are doomed to fail.