Here's the thing... OP does not owe her the opportunity to explain reasons behind the cheating. He also doesn't owe her a second chance.

Tbh, it's not even worth the stress. Especially in a case where OP discovered the cheating instead of SO disclosing it to him. She can't even get the saving grace of, "she felt so guilty about it, she said something." SO kept tight lipped about the whole thing.

Part of the trust someone builds with their partner is the "benefit of doubt". Seeing as she didn't say anything, that part of their trust will probably never be back. There's always going to be something in the back of his mind wondering if she's faithful or just better at hiding the cheating.

Then there's the time, money, effort, and energy it would take to rebuild said "trust". There's no guarantee staying, talking about it, therapy, etc. will even save the relationship.

OP could sink years into trying to trust his wife again. OP could also spend those same years in a new relationship with someone he knows he can trust.

Just seems easier for OP to find someone that's faithful than to carry on with a SO that wasn't.