Because he's a complete and total @$$hole, that's why. It sounds like he spent four years treating you like emotional toilet paper. You certainly had plenty of reason to walk away.
Burn that bridge to the ground: get complete custody of the kids (with his history of violence, that should be easy), change your email and cell phone, and move as far away as you can. He wants to be a jerk, let him, but you don't have to be around for it.
Good for you for throwing this waste of oxygen to the curb; now stick with it, no matter what.
Dan is right (as he is often).
Hey girl...sorry to read such a tragic tale...It would be SO easy to criticize you for your choices, but I see you as an empowered hero.
We all give guys "another chance", and you've paid your dues 10x over.
I say GOOD GOOD GOOD for you, for having the courage to get out. Many don't, and I think you know that. Some feel emotionally or financially trapped, and don't feel that they have anywhere to turn.
Will it be tough, and will you consider going back at least once? Probably. But know that this is a very harmful situation, that is best resolved with the support of friends, family, counseling and the law on your side.
If money is an issue to get some counseling, there is online assistance for domestic violence, 1-888-7HELPLINE. Please call them to get some guidance and support. There is no shame in asking for help.
Please know that your courage and strength will ABSOLUTELY help the next girl who is sketchy about leaving.
When you share your story, you spread knowledge. And you know knowledge is power.
Best of Luck to you.
I would suggest conceling too. Why on earth would you stay with a man that long and have his children when he treated you poorly. I am sure there were signs from the very beginning which you either didn't recognize or just ignored. No point in repeating the past with another jack @ss.
I don't see anything pointing towards happiness in the past...