he was cheating on her looooooooong before that... remember they was already on the outs. that's why she fukked owen.. that's why she signed the deed over. he was still out with the ho's and not coming home some nights
he fixes things, then moves on to the next thing.. remember he saved gillian when she was young.. he could have shut up and picked her up and dropped her off... nah he developed a friendship, made sure she was taken care of when the commodore didn't, and even raised her son. even now he lets her live even tho she was in on it
Who did he cheat on her with?
She cheated with Owen after her brother made her feel like shyt in NY. Nucky was going out scmoozing, cuz that was his job, but if you notice, he was always just entertaining the broad he was with. The random politician or businessman would be getting it in while Nuck's girl would be complaining he's no fun. Nuck was intent on becoming a family man after cutting off Lucy and coming to terms with his relationship with his father.
Not that it matters that much, since I don't have a problem with Margaret cheating. My problem is with her switching from saint to sinner, then back to saint, then back to sinner as she sees fit.