I'm not a cheater, generally. I've been cheated on repeatedly. I've only cheated when one person came waltzing back into my life. That was 2 times over 30 years. Should I have done it, of course not. We're married now and I'd never even think of cheating.
Some people will cheat no matter what. Some people have issues with intimacy or commitment. Some people are exorcising demons from past hurts. Some people are just players and liars. Others fall in love and like me were cowards until we weren't. Proud, no, but true, yes.