I think cheating is understandable in certain situations. It’s not right, but life isn’t always straightforward. I’ve never cheated and I’ve never been married, so I’ve got no agenda here. Just using my imagination.
Couple with kids own a house between them, both working, earning just enough to cover bills and mortgage. Neither of them could individually afford to buy a house big enough to have the kids stay over.
Husband’s job changes so he works from home, and doesn’t have to meet people any more. He stops showering, doesn’t clean his teeth, eats crap all day, gains several stone. Refuses to help with any childcare, doesn’t clear away any of his mess, doesn’t do any household chores. As soon as his working day is over, he sits on the settee drinking beer in the same clothes he’s worn for the past 2 weeks.
Wife is run ragged. She works full time out of the home, comes home to a mess every day, does all the child related stuff, all the cooking, cleaning etc, literally everything. She begs her husband to help but he says he can’t be bothered.
She assumes he must be depressed because he wasn’t always like this, but he says he’s fine, just says he’s enjoying not having to get dressed up for the office any more. Flatly refuses to admit there’s a problem. Won’t shower, won’t wash, won’t clean his teeth, won’t help out.
Eventually wife says she’s had enough, says she wants to split up. “Fine” he says, “but I’m not moving. If you want to split, you can move out”. Except she can’t afford it on her own, so she’s stuck. And she can’t rent a tiny flat, because there wouldn’t be room for the kids.
So they carry on as they are. Wife gets more and more depressed, holding everything together while her husband does nothing. Not sleeping because he smells so bad. No sex of course. She doesn’t find him attractive any more, because of the smell and the 10 stone he’s gained. And the attitude. Her life is pretty miserable, she feels exhausted and unhappy, and she can’t see an end to it.
Then someone at work starts paying her attention. He’s nice, funny, clean, attentive, interested in her, makes her feel like she’s more than just a skivvy. Eventually they start an affair.
It’s not right, but you can see how someone might get to that point.