There’s a chance the mother had been told that if she left, he would kill her and/or her parents and take the kids where no one would find them. Battered women have seen the violence these men are capable of and feel the risk is higher in leaving than staying. It happened to my sister-in-law and now her children resent her for not leaving sooner. She never told them about the threats because even though he was a monster, he was their father and she didn’t want them carrying that extra baggage. My sister-in-law gave up 25 years of her life to protect her kids until he finally left to be with his mistress. We thank God every day that he is her problem now.