I went through the EXACT same situation. After reading through the responses to you, I guess it is more common than I thought. I got home from work one day and he just said he was done. Later I got all the blame and he got all the credit for "sticking it out" (he got credit, at least in his own mind, not so much in the real world). He was living with OW 2 weeks after our D was final and they got married about 6 months after that. He has NEVER owned up to his share of the responsibility and wanted to lay it all on me in the beginning. The only way my sitch differs from yours, as far as I can see, is that my XH moved 1500 miles away from me to be with his OW (thank God for that not so small favor) and our children were adults when it all went down.
To this day, almost 4 years since our D was final, he has yet to acknowledge that he had any fault or blame in the matter. He still thinks it is all my fault and has sold his new wife on that. Funny thing, he was married to his first XW for about 17 years then me for about 9. So, the way I see it, since he seems to be halfing the time he's married with each divorce, this new skank has about 4 or 5 years total before he does this to her and moves on to #4. By my calculations, that leaves her with about 2 more good years. Cheers to them and their scheming ways.
I'm sorry you have to be here, man. Hang in there. I promise it does get way, way, WAY better.
Me 52, H53 Bomb drop 9/29/2014 Divorce from XH final 12/17/2014 Marriage #2 12/31/2019 5 adult (step)daughters (3 from XH's first marriage, 2 from current H's previous relationships) 6 grandkids