A high-conflict marriage isn't healthy for anybody. Nobody thrives in a toxic environment with a lot of fighting and yelling.
However, kids whose parents were involved in those kinds of marriages actually do better after their parents' divorce than kids whose parents sheltered them from the unhappiness in the household.
Kids are very adaptable -- much more so than many adults. However, they need time to make mental adjustments to changes in their world. When they know that their parents are unhappy and the household isn't thriving, a divorce is not only something they tend to expect, but it can ultimately be a relief.
That's not so for the children whose parents were "low-conflict" all the way until they announced that a divorce was imminent. When studied over a long term, kids who were surrounded by high-conflict marriages that ended in divorce did as well as the kids whose families remained intact. The same couldn't be said for kids who felt taken by surprise when their parents divorced.
Those children ended up developing serious trust issues. They essentially felt hoodwinked by what "looked safe" and stop trusting that things are as they seem in their own relationships. Since they believed that their parents were in a stable relationship and were deceived, they can't trust that their own relationship is stable -- no matter how it looks.
Essentially, it's better to let the kids in on the unhappiness in a household -- although you need to do it without being negative about your spouse or revealing "adult" information. Slowly breaking the news that your marriage is over to the kids definitely beats jolting them with the information out of the blue.