He might be healthier - but certainly not a better version?
Why do the supportive ones get screwed over?
I'll hazard a guess here, because they are the ones that are looking for a healthy relationship, where none is to be had? They look at a persons potential. Of course it's possible if the person enters recovery and all that entails, but that's not the story here and certainly not in many cases.
He was a liar and a cheater when he was drunk, he got sober, now he is a sober liar and cheater.
There is a thought sometimes that if he/she would just stop drinking! all would be well. That's just not really true in many cases.
I'm sorry you got hurt again. Trust yourself going forward?