Cheating is the opposite of pair bonding. If you can do it, there’s something wrong with you and the honest thing (they can’t be trusted in social relations either) would be to split up before straying.
If you’re a cheat, you aren’t monogamous. Monogamy is a bond. If the bond is broken, there is no relationship.
One minor correction: there is no evolutionary benefit for men cheating.
That is a myth. Based purely on pregnancy odds (actually rape leads to more conception, so that’s a dark path of naturalistic fallacies to argue), not the birth of a child or its own reproductive success (true success).
In fact, if you look at the evidence?
It reduces reproductive success.
Look at the children of deadbeat fathers for the social proof too.