Lots of wives would be okay with this! It isn’t a betrayal of trust, it’s not an open-ended arrangement with unknown scope and terrors, it’s plainly declared up front, it’s so infrequent that it has little to no risk of displacing the primary marriage relationship, it minimizes jealousy, it isn’t a side fling that could be stumbled across by accident in the everyday by the wife, it’s a controlled outlet for long-term desires, it’s not likely to cause financial distraction, dependency, or drain. And that’s just ninety seconds worth of solid good reasons :)

So what's the problem if the consenting adult is okay with their partner having a consensual relationship with another adult?

You've lost me here.

I can explain it.

There is something in it for the wife. The world is a bit more "House of Cards" than some people assume. Aside from the French and a few others, western cultures seem almost uniquely dishonest about the tacit assumption that successful men will have mistresses. This isn't a new thing. Warren Buffett was essentially married to two women most of his life and no one cared.

Many wives highly value the accrued status of being formally married to a high-status person. You can take half the money but the social status doesn't follow. No one cares about a billionaire divorcee with no status beyond a bank account.

Why not? They’re both grownups with brains to think for themselves.

Ok we’re back to pitchforking (possible) open relationships now? You know very little about their dynamics. You lack information and frankly any justification to judge.

Billions, remember?

She should have an equal provision about her special friend. Or a personal trainer.

I don't know about their specific arrangement, but in some relationships, having other partners is not only accepted, but actively used to reinforce the primary relationships.

If you accept your partner has those urges, you can either treat it antagonistically and have those urges become a problem in your relationship or you can absorb them into your relationship and have it be strengthened by them.

You either become the one being cheated on and weakened or the one in control with a relationship strong enough to not be threatened by some side action, which in turn makes you a rarer and more valuable mate.

Or as a less cynical take, there's also the phenomenom of compersion, the ability to feel joy from a partner's happiness with other people. If you truly care for somebody and want them to be as happy as possible, you might be willing to set your ego aside to create that experience. And of course, that sort of security is again very attractive and a rare trait in itself.

I remember reading about an email he sent to the "special friend". It definitely felt like she wasn't okay with this.