It may look easier to keep on walking, but he's going to pay less for just taking his shame for the short while, and it seems like you will support him and not hammer him over the head wit hit - then continuing on and taking hell for who ever knows how many years. For me, everything I did before has basically been destroyed.
Plus, this guy may lose the female after the divorce, because she's going to demand more of him. His appeal will drop because the competition will go away after the divorce.
Also he has to wonder if the female just enjoyed messing with a married guy, and once not married that fun is gone.
Or even for some people it is their job to break up relationships, and once the job is done, their done.
Or it may have been their personal challenge, to get this happily married man out of the house.
Too many risks, and what sounds like a wholesome and loving wife. I wish mine talked like this about me behind my back.