iirc we know that social media use leads to dissatisfaction due to seeing everyone's "perfect" lives. Perhaps these married people are observing "perfect" marriages and taking a negative perspective on their own?
My interpretation is that social media use leads to ambition and raises people's standards. Seeing other people doing better makes people think about how they can improve their own lives, which leads to less complacency and drives them towards positive change.
I am going to go out on a limb and say that most relationships are crappy. If the average person was to see what a good relationship looks like, they would leave or try to change their current one, which is a good thing. Same applies for careers.