I'm no psychologist/psychiatrist, but I think people stuck in these abusive relationship cycles aren't much different than an addict. They know it's wrong, not healthy, dangerous, etc., but in their minds, they somehow justify it as normal. I think we've all known someone kind of like this, maybe even a family member (or two), who cannot seem to make a right turn to literally save their lives... they're somehow compelled to drill holes in the bottom of their own boat, don't want to drown, but don't want to be rescued either.
Knew a lady that cycled through abusers.
After a while we stopped reacting to her "Needs" and she sought out other places to be the center of her self generated pity posse life style.