Do some research on “silver divorce” is what I think it’s called. Unfortunately this isn’t uncommon so you may find plenty of good content. What’s bittersweet is it’s also common for there to be regret after the fact. But once you’ve already peeked behind the curtain you can’t unsee what’s been seen.
Sorry to hear about this….but when I continue to hear stories like this it’s hard to act surprised anymore. But it’s sad that there is emotional damage on their end and even for you. It sucks.