Is Jeffs the only lawbreaker in that cult? I don't think so, and I doubt the authorities do, either. When young, indoctrinated girls are assigned to marry some older man, or for that matter ANY man, that man deserves to be prosecuted.
The adult women who quietly stand by and allow this to happen need to be charged with a crime, even if they had the same experience. This is a sick social group and maybe some jail time will bring them to their senses.
If they did, in YFZ case in Texas, they didn't put anything about any other independently developed evidence in the affidavit for the warrant to search the ranch for "Sarah", and to arrest her supposed "husband", a man known by the local Sheriff to be in Arizona and in frequent face to face contact with his parole officer in Utah.
Hasn't so far. They and their predecessor groups have been around since the LDS abolished polygamy, in the 1890s. They've been bumping heads with the law every since. Other than the polygamy, their age of marriage wasn't that much younger than in the larger society until fairly recently, when they got a bit younger, maybe due to earlier menarche in the females, and of course in the larger society, marriage ages have gotten much older..in general and when the females bother to get married at all.
Maybe there's another way to bring them into the 21st century, but I haven't a clue what it might be. You might get them to give up marriage at ages younger than 16 (the law in Texas, with parental permission) but getting them to give up polygamy is going to be a tough row to hoe, because it's too entwined with their religious beliefs.