The form of government changes after wars ALL the time. This is not a new concept introduced by this show. This last greatest war changed many things, including peoples attitudes and character. The elective monarchy that was established with Bran makes total sense if your breaking the wheel and leaving the patriarchal monarchy behind.

For me, the character arcs in this series made sense as you saw people grow and change. Sometimes into characters you might not want them to be, but nonetheless characters that made sense for the story line.