Wife is probably oblivious. Most people aren’t that attuned nor observant as you (and me.)

Or she knows he’s a cheating bastard (most likely has done it before) but looks the other way cuz likes their cushy life style.

It’s always a shock when find out a friend or someone you know is cheating on their romantic partner.

Imho, the easier, simple, honest and best thing to do is just break up with current person FIRST, then go be with whoever you want.

Cheating on a romantic partner is a CHOICE, a selfish one that will cause lot of harm, esp if there are kids involved.