I have to agree, my parents' marriage was really unhappy for a long time, and it definitely affected how myself and my brother viewed not only marriage but relationships, the concept of love, and the opposite sex. My parents eventually worked through their issues and salvaged a relationship, but I believe it did take a toll on their health, affected their outlooks on their lives, and again, it negatively impacted their children. I love my parents, but I can say that they would have been better off divorcing, and most likely we their kids would've been better off too. Anecdotal evidence, sure, but I can't imagine it could ever do much good for kids to watch their parents be miserable and just go through the motions out of habit or expectations.
As for the article, it sounds like they were in dysfunctional marriages and didn't/don't want to either put in the work to fix it, or dissolve it and be free to either look for the kind of relationship they want, or date/explore. Or they needed an impetus/excuse to leave, get divorced, etc. It happens this way sometimes, and it's pretty shitty for the other spouse, but people can be quite selfish, it's even stated there in the article. Not much else to say, really.
I think a lot of people don't realize or should I say refuse to realize that, that a bad relationship is going to be awful unless you both either work on it, or you break up. It's even worse when people throw kids into it, you know the classic "band aid baby" situation. Marriages and kids aren't fixes, they're complications, albeit usually wanted complications.
Some people just put too much pride, ego, and stubbornness into this idea that being in a relationship, or in this particular case, marriage, as some penultimate goal, instead of something you might do when you find someone with whom you'd like to commit, that is, if you ever find them and have that mindset. These are also the people who constantly seem to have relationship issues or seem unhappy, imo.