What is going on with women who refuse to leave an abusive relationship? I am seriously starting to believe it is some sort of disorder. I don't mean to insult anyone or judge them. No one knows what someone else is going through unless they walk in their shoes. I am genuinely trying to understand. How can people help?

I had 2 friends who were amazing, smart & stunning women who stayed in abusive relationships. I genuinely had no idea at the time. I was young & didn't recognize the signs of control/manipulation. My husband did see it. I slowly asked indirect questions & would let them know they could stay with us. Both are now in healthy relationships. Only 1 did we help.
My MIL is a different story. She is a closet narcissist & I think she enjoyed the attention she got from it. She grew up in an amazing home & was offered a place + financial support to leave. She still wouldn't leave even for the safety of her children. My husband knew I would absolutely leave if he verbally or physically touched myself or our children. He broke the cycle b/c he understood.
So maybe teaching abusive red flags & listening/being there if you see it?? Doesn't sound like nearly enough.
Yo the victims, please know my ♥️ is not that I like it happened, but that you are loved, valued & supported.