You talk about "extreme ownership" but you won't let the cheating spouse own to get mistakes ("alcohol makes you do things you wouldn't", ... I'm not going to repeat what that other dude said because he addressed all your points very well).

We get that everyone would benefit from looking back on one's actions and life and looking for where it went wrong, how one could have prevented that, how to be better in the future, ...

But that dude is not there yet, and he doesn't need to be. He just learned that his life partner for a long time betrayed him. Maybe in a year he'll have grown from it, maybe he'll learn to forgive her and their couple will be stronger than ever. Or maybe he'll cut her loose and will start his love life anew and will be better prepared for the next relationship.

The thing is, there is no blame to place on him for the cheating, that was the wife's fault. And you're expecting him to be at peace with what had happened even though for you it took a year or more. I think I get how you're trying to be helpful, but you're not really. He'll have his own path, putting the responsibility on him or trying to make him see the "good sides" of this extreme betrayal is not fair.