Being abused doesn't start all at once, or over night. You don't have a date with someone who then screams at you over dessert and ask him if he's free next weekend. He's a gentleman, loving, and everything you think a good person is. The bad things happen slowly, and the appologies are so profuse and seeminly sincere that you believe him and stay.
And after awhile, you get desensitized to the littler things, and then worse and worse. But I think there always comes a point where he crosses a line so severely that you can't look back or forgive. A lot depends on local support, not strangers but family and friends. You see, it is easy to say "he's treating you badly, get out!" But when you do you are beset with people saying, "was he REALLY that bad?" or "what about your children?" And even if they support your decision to leave, a month or even weeks after you've left your nightmare, they're over it and you aren't. So if you mention it, or talk about what you're going through you get hard looks, exasperated sighs and "can't you just let it go already?"
Easier said than done. The fact is the support everyone says is there is largely words and little else. And what little there is is tired of the drama after a short time.
It takes immense strenth to leave - and to stay gone. A person should never be minimized or degraded because they were fooled by a master manipulator; rather they should be applauded for seeing through the facade and leaving the nightmare. Even more so for rescuing children from that hell.