When you get married, you aren't signing up to be a caretaker to a mentally unstable spouse. If your spouse is harming your children, it's your responsibility to get your children out of that situation however possible. There are thousands of legitimate situations that you'd agree are worthy of divorce.
There's a lot not said in this article. It's completely possible that he and his wife weren't well suited for each other to begin with. Roseanne was on the air for nine seasons. That's a lot of time to build resentment and hatred, if that's what was happening. Maybe the two years where he stayed at home let them figure out just how much they didn't care for each other. There are lots of legit possibilities.
It's not as simple as not living up to your commitment.