It really doesn't matter what his reasons are, or how he did it. The divorce is happening, and someday you may see it for the freeing gift that it is.
I also suggest Al-Anon, because it's pretty clear to me that living with an alcoholic has screwed up your thinking. That is NOT a criticism--I've never met anyone who has lived long-term with an active alcoholic who didn't learn some messed-up thinking as a coping mechanism.
Hugs, stick around here, too--you will learn a LOT.