Hard to make your kids homeless and live in abject poverty after just one slap. Easy to say it
This^
If she could easily leave and be financially comfortable with without him, he'd not be abusive, they start, -the predatory instincts kick in- when they are in a position of power. It's not until she is trapped that he starts getting the urge to exploit the situation, he wants to increase the feeling of power and domination, he cant get that feeling if she can easily up and leave and have a comfortable life without him.