Many think that infidelity is a problem, but it is more often a symptom of a bigger underlying problem. Symptoms tell us there is a problem needing attending to. For example, if you have a sore throat you should rest, drink fluids and take some aspirin. If you press on through, chances are your cold will be twice as bad. Infidelity is like that. There were probably symptoms long before the first act of indiscretion, but no one was looking or listening for it.
You can go on and on looking for reasons why couples are unfaithful to one another, but what you should do is search for the root or roots of the problems, and then to build an intervention. When you are in the middle of this kind of emotional uproar, you aren’t always capable of thinking clearly on your own. You need the objective guidance of a professional trained in helping families heal from psychological assaults. Plus the natural tendency of all families is to cover up problems in the mistaken belief that doing so will keep the family safe.