he was married between 2012-2017. i figured he was seeing someone off and on between 2015-2017. it would have been really private and his wife never knew about her. i think it would have been a little deeper than just hooking up, but the marriage obviously trumped whatever they were doing. fast forward to his wife finding out about a different indiscretion and the marriage implodes. i think it might have been assumed on the girl's end who he was seeing, that since the marriage ended they would have ended up together. he decided that wasn't going to be the case, and ended their affair rather than getting into another relationship.
sorry for the ramble and if that doesn't work, we can brainstorm something different!