Why did my ex boyfriend apologize for what he did? Easy 10 points!?

My ex boyfriend and I broke up over a month ago, we dated for over a year and were each others first loves. After we broke up he became very angry at me for no reason, lashed out, and said some hurtful things. We haven't spoken since, and three weeks later he sent me long text saying how sorry he was. He's never one to apologize or admits he did wrong. But it confuses me because my friends told me all this week he has been drinking, smoking, and being intimate with women so why would he apologize for what happened three weeks ago when he's having fun? We're both 20 and had a mutual break up.