Roll the dice…take a guess…the answers are assuredly varied. Best place to start is to ask them.

Human psychology is a funny thing. I can think of at least two explanations that might seem like good reasons to a person still reeling from infidelity. Sometimes, when people can’t get even with or get closure from the person who wronged them, they decide to get even with or get closure from the universe. They want to balance the cosmic scales. How do you balance being cheated on? By being someone else’s adulterous fling. It may not make sense to us, but it might appear to make sense to someone who is still suffering from emotional shock.

The other, slightly more grounded reason is to reassert one’s desirability. Infidelity can be a huge blow to one’s self-esteem, and the easiest way to restore it is to prove that someone is willing to cheat on their spouse for you. This establishes that you are just as desirable as the person with whom your spouse cheated on you (or close enough), and so the problem is obviously with your spouse and not with you. So having an affair with a married person can help someone get over the insecurity and self-blame that so often follow the discovery of infidelity.

Maybe the infidel is a liar and their spouse never was unfaithful. Maybe their spouse divorced them for being unfaithful. lol

Nope, I am pretty sure he did it. He moved in with his fling even before the divorce was finalized. I think it is probably something along the lines of the second scenario mentioned by @SavoirFaire. She was pretty devastated at the time and I can see how she would be looking for something to boost her self-esteem.

I agree with @SavoirFaire‘s answers, and would add that it’s easy for people to be self-righteous until they are themselves tempted.

They’re feeling vulnerable, insecure, rejected and emotionally at sea. They may be feeling numb and the person they have the affair with makes them feel wanted. They want to escape from their reality. There could be a million reasons. They might not be good reasons and they may not be fair to the other person’s partner, but people do crazy things.

31:6–7
Give strong drink to the one who is perishing, and wine to those in bitter distress; let them drink and forget their poverty and remember their misery no more.

Because “it is only bad if others do it.”

Maybe the married coworker was pursuing the person and made the whole thing very exciting and easy. Fooling around with someone who is married usually is a sure bet there are no strings attached, and a lot of divorced people, especially women, don’t want to think about a relationship or another marriage when they first get divorced.

Plus, screwing around themselves with someone who is married gives them insight to the whole cheating thing. They learn people don’t usually cheat to hurt their partner, even though that’s what winds up happening, but it’s just a selfish act to boost ones ego, or feel carefree and desired again.

It’s pretty awful to do it though. You would think someone who has been hurt by infidelity would not do such a thing. It might be an indication of why the marriage didn’t work.

How sad. What does love or the lack of it do to us?
Perhaps it causes us all to be able to do some things, that no one ever thought that they would.

Because a heartbroken person does irrational things. They are also less likely to value the concept of marriage as much as they did prior to their partner’s infidelity. It is easy for an experience like that to make a person jaded and callous.

Because the disappointment and disruption of divorce is not enough misery. Now they want to lose their job too.

@BlackSwanEffect I can see that the marriage concept would suffer. I have a friend who divorced and later re-married to a woman who had done the same. He told me that in his second marriage they had both learned to tread more carefully because they both knew that they had survived divorce once before and could do it again if pushed too far.

People are not logical and they do stupid stuff all the time. Save your time and brain power and don’t try to make sense.

I would assume they figure something like “if someone could do it to me, why can’t I do it also? Why do I always have to be moral? No one cared about hurting me so why should I care about someone else.”
A small part of them probably wanted to understand what their ex had been feeling before the divorce.