Sometimes, the reasons are obvious, like addiction or physical abuse. Other times, the roots are more complex. Fixing a marriage is not like changing a tire. The marital meltdown usually starts years before the breakup. Many people don't have a lot of choice.
Some couples can resolve a conflicted marriage.
Others have to dissolve the marriage to resolve the conflict. The book marshals impressive statistics on why being married is good for you. We want a good marriage. The authors believe that the majority of couples that split up are not that unhappy. The ones I talked to were desparate.