In many cases, when a wife is unfaithful, her affair may be a ‘tit for tat’.
Hubby has/had an affair, and wifey went out to not be Home Alone. Unexpectedly, unsolicited, Wife met someone, or upgraded a casual friendship.
Her marriage is whatever it is; and she is not going to sit home and cry and berate herself when she can be out, and feel desired.
In many cases the wife’s lover is either younger than her, or not ready to settle down, or in some kind of flux situation where having a serious relationship is not on the cards.
In many cases, the man who is having an affair with the wife is doing it deliberately to elevate himself above the husband.
Hence, a simple affair is what he desires, what wife desires, and a good time is had by all.