Marriage vows have little to do with any of this. There are simply people out there who have severe mental issues or moral issues or who are too imature to realize how hurtful they are being. They have them even if married and sticking it out for the sake of the kids is sometimes the worse thing you can do.
The cp in our case did some of the things she does now WHILE they were married. my parents tried the whole "stay" together thing. WE were so HAPPY the day they announced their divorce. Neither of them was really wrong, they simply didn't mix well long term.