It is nice to know someone is dealing with the same unbelievable situation.
My H, as far as I know is “single” lol. In the beginning, when I found his fake Facebook showing his “fiancé” I would check almost every hour. This was when he was in his work trip that was three months long. After a while, (and therapy) I slowed to once a day. He wasn’t thinking of me, so I needed to put all the energy onto me.
Therapy can’t answer why, but I’ll tell you my therapist’s suggestion; OW is the same age I was when we got married. My Therapist says, that he is chasing how he felt at that time in his life. Sometimes I even see a younger person in his behavior, like a teen-trash laying around and not thrown away. Clothes piling up. We finally came to an agreement about the laundry. If he needs it right away, he can do it. If it is towels and something I am going to wash anyway, I’ll wash it too. I won’t put it away and I never take anything into the room he is staying in. That’s his choice to isolate, so I am not going to help his isolation along.
Your H moved out, mine is still here. Either way, we really don’t know what they are doing and what is going on in their minds. To help with detachment, find something YOU like, with stay in place orders, you really can’t go anywhere, but a puzzle, reading, computer class, a tv show? These little things have helped me find things to look forward to.