Did he get caught then and suffer actual consequences? Because if not it's not as if character development happens automatically, especially if there are significant gains to be had from cheating.
I don't pretend to know what causes people to change, so I can't answer your question where it seems like you're implying that he would only change if that was the case.
All I know is that he admited to it, so if that's "getting caught", I imagine he has receicved consequences from his admission.
