I can well understand how someone does not understand if they have never been in that situation.
How can they.
Obviously there are different levels of deception but to be betrayed I suppose has many different facets to it, I must admit I did not really think about the ow, you don't at first when you don't know who they are and then when it becomes apparent you really are just dealing with your h's deception.
In many cases though there are many cat and mouse games before the ending of an affair, so much gaslighting which in effect is the h and the ow purposefully constructing situations, and lies to carry on deceiving the outcast sat at home usually with the children. That hurts like no other pain.
I should imagine if you were to compare to get the feel for it it would be akin to your best friend at school actively cutting you dead and finding a new best friend and then turning other friends away from you to allienate them.
Very basic deceitful behaviour that is a shock to many wives who would have never believed was possible from their own best friend. It's probably during that cat and mouse time the most ammount of damage is done, as Wookie says it depends on the actions as to whether they stop, consider your feelings and then feel remorse, many do not.
That period whereby the ow knows that the wife knows is even worse than before when they were deceiving without knowledge. I know for a fact my dissapointment was in his ability to get swept up in this new found friendship that was based on ego, sex and a sadistic need to get one up on me, it was as though it was addictive to him, not so much the ow but the game.
Very disturbing stuff and something I think which even shocks many ow and betraying husbands after the event, the level of sneaking arround behind someone's back, badly, whereby they both know the wife has suspitions, and that happens daily, hourly by meetings and phones. It's a terible thing to do to someone, women have been driven mad by it.
There's the point where probably wives develop that hatred for the ow, a persistant ow, one who does not back off or feel shame or basically care, at that point the wife has probably dehumanised her because the ow has dehumanised the wife.
So when it's all over, marriage ended or not, children devastated, extended families torn apart and the dust settles is it at this point that ow wish for mercy from society not to be so harsh on them, why do some care ?
My h took years to understand that his behaviour was abhorant, not just in the affair, sleeping with someone, thinking he had found a new soulmate/friend but how the dance played out, the lies the cruelty of one humans behaviour to another.
I though he was better than that, my miscalculation, I can sometimes see the disapointment in himself, the shame, disgust call it what you will and it's also seen by his children.
Whether that shame is there with ow who actively know what they are doing to another human, I don't know, some seem very defiant about their actions, some wish to forget and some genuinely feel sadness in how they have behaved.
I also think there is a fear when they are settled that it never happens to them, they think they know the pain that's involved but they really havn't a clue.