My first question is, why do women always blame other women?
I mean, if your partner cheats on you, he's the despicable one. He entered into a committed relationship with you. The other woman? Unless she's one of your friends, she owed you nothing.
My follow up question is, why do women think men with healthy sex drives will be happy to stop having sex for years?
If you had sex with your partner regularly and then suddenly stopped, doesn't it make sense he will still want sex? As a woman, I think it's perfectly reasonable for a woman to go off sex when she's pregnant, has recently given birth, or even is a good few years postpartum. Women go through enormous physical and emotional changes, some which are incredibly traumatic, painful and/or dent their self-esteem. Their bodies change. The way they think changes.
Men? Well, they don't go through any of that. I suspect a lot of them don't believe how horrific it can be, because they physically cannot go through any of that. I think they justify cheating to themselves because they're not having their physical needs met in their existing relationship, even though it's not reasonable for them to expect those needs to be met at that time.
As a woman, love and sex are intermingled for me. It's the way my brain is wired. I think a lot of men can compartmentalise those two things, and can see seeking sex outside of the relationship as not impacting on their emotional connection with the relationship.
I don't condone any of it, but OP, you didn't ask about whether I agreed affairs were OK. You asked to understand why they happened.
I think ultimately, it all boils down to men thinking they're owed a shag by someone. Anyone.
PS My ex ran off with another woman. I've reframed my thinking now and I understand that she didn't owe me anything. She probably didn't even realise I existed. All of my anger and hurt should have been towards my ex. Not that I care anymore now, because I've moved on. But I am absolutely zen-like when thinking about her. Women need to stop blaming women for the shitty things that men do.