Polygamy works for our lead character Bill. It also works for his three wives and his children. They consider themselves law abiding, family oriented, god centered people. Thus, Bill wants to come out of the shadows and be accepted for what he is, a polygamist. Thus, this final season is primarily a tragedy on Shakespearean levels because he and his family can never be accepted in this country for what they are. This is because even though they live in the most religiously tolerant nation in the world, which also confers the greatest personal freedoms upon its citizens, that county can never allow polygamy to come out of the shadows because it is against our law.
Utah was permitted to enter the union only if it ended the practice. And it is clear why the country insisted on this: it is a nation of laws and too many legal problems are potentially created by polygamy, especially for a modern society which confers equal rights and responsibilities upon its citizens. This practice worked somewhat in an agricultural society centuries ago. It is too much of an anachronism for a post industrial revolution society which has marched off into the digital revolution. Just look at how little educated his entire family is. How are they going to fit into this modern world? He is very rich through most of the show and it is pretty clear all of these children will NOT be going on to college. I can't recall any of these children ever using a computer of any sort. Are they all going to sell washing machines at the family store?
It never occurs to Bill to ask himself how he can expect his store patrons, his senate colleagues, his neighbors and other acquaintances to feel when they see him and his family prospering although they are flagrantly breaking the law. This would certainly occur to even the average mafia don, even though one doesn't think of such a person as sensitive to others' feelings. It would occur to him as a matter of his survival. However, Bill is so caught up in his religious vision that his survival instinct seems deeply tamped down or even turned off.
Bill believes is it possible to bring polygamy out of the shadows and into the full light of both the law and the USA. He couldn't be more wrong. As he keeps fighting to achieve this, one disaster after another befalls his family as other people and factions want to bring them down. Bill Paxton does an extraordinary job with this character. He conveys him as a good and spiritual man, trying to do the right thing by everyone in light of his own religious beliefs. Yet the fact that he can't perceive that this single mindedness enrages others to the point of violence does not deter him. He is myopic beyond belief. It never occurs to him to ask how someone else might react to his paternalistic actions. And this is his fatal, Shakespearean flaw.
The three wives come off very well in this final season too. They have always had clearer vision than Bill about their effect on other people. However, they support him in his beliefs and share his overall faith. There is no question that they are capable of enduring and most likely will always endure together.
On an ironic note, early in this season we see Bill and his family still trying to make the casino with the Indians work. Ultimately, Bill and his family are too much for even the Indians. These are the same Indians who live on reservations, run gambling casinos, inhale crystal meth, have serious alcohol problems, etc., etc., Yes, the Indians are different from us but they don't seem to be on a different planet like Bill and his family seem to be. (The Indians also act within the law with what they are trying to achieve overall with their casinos so the government is not against them per se.)
I felt the show very satisfactorily concluded. It was a good point to conclude it as well as there was not much more to be done dramatically with this family without making it into a soap opera. There is something to learn from Bill's fatal flaw: no matter what one's personal religious beliefs, one cannot put blinders on to what is happening to the people in the larger community of man. To do so is to utimately welcome chaos into your life.