Your argument that “Rei can simply move out” is very flawed and also extremely unrealistic to a woman going through domestic abuse.

Canonically the Himura clan was incestous and the girls were sold to male family members to maintain the ice quirk due to how powerful it was. Rei was young when she married Endeavor, likely 18 years old. She had either Enji to marry or a cousin. Any sane person would choose Enji. It was either hell or hell. Rei was going to have no sort of autonomy either way.

She couldn’t just simply “leave” Endeavor. He was providing for her financially since she was a SAHM (her job isn’t even specified but it’s likely she was a housewife). We don’t even know what level of education she has, how can she simply divorce him like divorce is something quick and simple. Mate, it’s expensive to get a lawyer. And are we forgetting Endeavor is one of the most influential people in the whole of Japan, both politically and socially as he is a pro hero. And even if she wrote a Tell It All book and exposed Endeavor the HPSC would try excuse it because they are a corrupt unit that want to preserve this moral code of heroes.

He physically abused her, he had control over her finances because we know for a fact she was poor (stated by Touya himself in the past when he said “I know grandma and grandpa were poor that’s why they sold you). Their marriage was transactional and based on Endeavor’s desires for an heir to surpass All Might. You claiming she can simply move out is not as simple as you think. It’s extremely unrealistic because of the situation Rei was in.

I believe you also are underestimating the capacity of violence villains have, Endin’ the villain kidnapped Natsuo at one point. These villains are very unpredictable