Affleck is, and always was, a cheater (and not long ago it was with the kids' nanny). He and Jen got together by cheating. So, I don't really care if he cheated on her. That is how she got him. And, I think she also cheated on someone to be with Ben. She was just very good at playing the nice wife and mum, lots of money to gain from that facade.
She is probably the one who does not want the divorce. Around here everyone knows who Ben Affleck is, but pretty much no one knows who she is. He is world wide known, from what I get, she is well know, or sort of, in the US.
Also, very rich people divorces are complicated. Lots of money, assets, etc.
Why LBS on HS worry so much with cheating Jen is a mystery to me. She was OW. Any OW Ben may have is what she was when they got together.
Sometimes good things fall apart so better things can fall together. (Marilyn Monroe)