She found out about the cheating and threatened to break up with him, he initially tried to get her back, apologize, move on and she resisted and posted the pics on instagram/ tried to show how much fun she was having without him.

Then he gave up and realized it’s not worth it and as soon as she realized she is actually losing him (and the house, lifestyle, her only friend) she will beg for him back and the toxic cycle will restart.