When young people are abused or neglected, it can be hard for their minds to come to terms with the reality of it.

Many reenact the behavior. That's why you often hear of the abused becoming abusers. Reenacting gives then some sense of control again, and tries to make the reality make sense to them.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3330499/

But as they grow older, like your friend, the brain develops, and perception becomes better. They have a chance of catching themselves and changing for the better, like your friend.

Some do, and some don't. Imo it explains a lot of the people in prison. They were not able to catch themselves, so society eventually had to.