susy, sorry you are here. But you came to the right place!
I would encourage you to let go of the need to understand. You never will. In fact, my W came through her wayward period, and now looks back and doesn't even understand it. This new guy your H has become is someone that even your old H wouldn't understand.
My W did things that she was morally opposed to before, and is morally opposed to now that she is through it. No one, not even her can understand what she was doing, the whys. All she knew is that the activities she was engaged in were satisfying some selfish need at that exact moment.
How about susy? How is she doing? Are you GAL? 180ing? And you need to study detachment and self-differentiation. You have allowed your happiness to be tied up in him and here is the thing: you can't control him. You have control over only one person. Yourself. You have control over only one person's happiness, your own. Your daughter CAN have that again, but that is up to you. It has nothing to do with your wayward H. And you can't control whether he reengages with your family or not, but you can still make sure your daughter has a loving family, even if that is just you.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018