This reminded me of the tekashi 69 song LOL
They probably never had any kind of clash with their personalities before their marriage since they're so lovey-dovey then. Ch 77 just proved how oblivious they were when they were together pre-marriage.
You're right. They could forget about anything and everything because their friend was making their life easy. They didn't love each other because of who they are, they loved each other because it was easy for them to do so. Now that the prince knows his wife is incompetent, he wants someone else
That's how most relationships are anyway. You see so many people have long relationships but can't continue a long married life
Dude married a religious zealot who doesn't want to have children and he thought she'd make the perfect crown princess?? Are you dumb or are you DUMB no wonder their marriage is a lost cause in both timelines