I've surmised from watching Sister Wives and Seeking Sister Wife that a plural marriage or polyamory model works only under very specific and unique circumstances. Considering how many monogamous marriages end in divorce, it's not at all surprising that relationships involving multiple partners would eventually crumble. One person has to work diligently and consistently to meet the emotional needs of one person, let alone two, three or four. Eventually, someone will end up feeling like they're not getting equal time, equal amounts of love and attention, equal value, etc. They show that one family on Sister Wives where it seems to work. I think the difference is that they all live in one house and the wives are totally on the same page, truly like and support each other and work together to make things work. It also seems like the husband is willing to change and bend to different circumstances and listen to his wives, rather than act like an authoritarian narcissist who says "it's my way or the highway." Kody was never the right person to take on more than one wife or have 18 kids. He's just not capable of giving that much of himself.