In a marriage it takes two to tango. When there is much communication, it is hard to miscommunicate. They should work hard to get each other to build on the relationship,not to let anything hinders. It is not one thing or two that can cause extramarital to happen. Something was neglected, something was not taken care of, something was not talk and verified.
It's just a relationship that was not talk over. If one apologise, if one explains, if both needs met, they can still move on in life. If they remain silent, not willing to let go or forgive that's how it will stay. This lets people around to be careful not to step into such a minefield.
It is not about good or bad.
Divorce doesn't destroy life. It is just a relationship. There's so much of skills to acquire, so much work to be done, if the life partner doesn't want to be part of his life, his love for her will never change no matter where she is. He can still show love to her and win her back.
But he just stayed and not move....