My in laws were just like your wife's grandparents. When they announced thry were getting divorced it rocked everyone. They were June and Ward Cleaver, how is this possible? Because they hid it. Nobody knew what was happening behind closed doors. Their children have issues because of it. Their D is now divorced and their S is on his way down that path too. They never taught their children conflict resolution snd look where it got the entire family.
You know, I never correlated the two before. My ex and her sister are now both divorced. Like yours, the ex's grandparents never showed them what was happening behind closed doors. I think maybe one reason was due to them rescuing the two from their terrible situation and taking them in to live in their house...I guess so they wouldn't see conflict and all. Maybe to shield them? Who knows. But they never taught them that important aspect in life. Just as you said, now look at where it got them. Even the ex's half brother and sister are divorced at least once. That ENTIRE family is a mess. And I fear it will seep into the children's lives.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.