This happened to DH's cousin. His wife left him for someone else, and that someone else then left her three weeks later.
It's a shame, they have children, and DH's cousin was devastated, but they are both happier now. She, at least, must not have been happy in her marriage, so although she didn't end it in the best way, it's probably better than her staying in marriage she was unhappy in, with a man she didn't love. Better for both of them in the long run.
He is in a good relationship now, his ex-wife is still single but seems happier.
If you really feel your marriage can't be saved and that divorce was the right thing to do for more reasons than this other man, I think you and your husband will both be better for it eventually.
As for the other man, you sound like you've had a lucky escape. Better to be alone than with someone like him. Maybe taking some time to be single will benefit you in the long run, and make any future relationships stronger as a result.