Why people choose to remain with abusive partners, or break up and return are so varied, different and nuanced, it's impossible to narrow it down to one or two reasons.
However one reason which I think has at least some merit is that some women actually enjoy and "get off" on playing the "victim."
I put victim in quotes because in truth they are NOT a victim at all, they are making a conscious choice to stay, to relinquish their own agency which on some level could be considered a manipulation and/or in part gaslighting in its own right. Or both.
Sounds odd but they feel empowered by it; there is a great example of this in a powerful HBO series called "Big Little Lies" (season 1) specifically Celeste and Perry's relationship.
Celeste (Nicole Kidman) admitted as such to her therapist. She would subconsciously (or consciously?) provoke Perry, pushing his buttons, in one scene Perry actually screamed "Do you want me to hit you"!!?
She admitted in therapy she did as afterwards when he came crawling back, begging for forgiveness, she then became the powerful partner in complete control of the situation and him. It's a toxic dynamic but very real in some relationships where abuse is present.
From the Centers for Domestic Violence in my local area.
>>"Playing the victim can be a type of learned helplessness, something that can point to a case in which abuse has been present, or a kind of manipulation where the person being abused is minimizing their contribution to a situation for gains.
Sometimes, the reason they do this is to play on other people’s tendency to be caring, because when someone hears a sob story, they often express support, feel empathy for the individual, and want to help them. People also play the victim to avoid taking responsibility for something happening in their life. They prefer to blame others [i.e. their partner] instead of taking action to improve something [or themselves].<<"
There are many stories I have read about and personally observed, attesting to this.
Something to consider.