...there is no sense of commitment anymore.
A friend and I were talking about relationships and why some of them end. We agreed that one person's bad behavior doesn't always result in a divorce/ending of a relationship. There are many marriages where one person is not behaving respectfully towards the other spouse, whether they are cheating, have an addiction, non-contributing, bad attitude, short tempered, etc. But the spouse stays because they feel like the bad spouse is still committed to the relationship. This is in addition to all the other complex factors: family pressure, financial reasons, don't want to be alone, etc. However, all those other factors become irrelevant the moment one person feels like there is no commitment from the other person.
It's a very complex subject. There are people with a very toxic partner but they still have a feeling that this partner is committed to the relationship. Their bad behavior is just that "a behavior", but not necessarily a full reflection of how they feel about the relationship. For example, people with a very bad temper don't necessarily want to break up even if they are easily irritated by their partner. Cheaters also don't necessarily want to leave their current relationship. This may be why their spouse chooses to stick around and hope that patience will eventually pay off - maybe they can stick around long enough to see their bad partner change. But if that bad partner starts to give off a non-committal energy, the other partner will start to let go. This explains why some couples break up even when there is no betrayal.