My mother doesn’t want to divorce though she is struggling so much

My family has only a few members - my parents, me, and a younger sibling. I am married and live separately from my parents, but I visit them on weekends.

My sibling works far away from home and rarely visits our parents. I always try to convince my father to give up smoking and drinking and to treat my mom better. Yet things don’t seem to improve. If anything, he just keeps getting worse.

Things went too far today. Mom was just hanging out with her friends, and yet my father got so angry that he poured gasoline in the house and threatened to burn it down.

There are many other horrible things he does that I can’t describe here. I tell my mom that she should divorce my dad, but she doesn’t want to. She keeps tolerating this horrible situation.

I really don’t understand why she behaves like that. I am very concerned about her. What should I do, dear readers?