It’s entirely conceivable that one of these two things were possible:
1. The breakup was what the dude needed to get his shyt together.
2. Maybe the relationship was stressful to breh and it numbed him out, making him just want to smoke weed and do nothing.
Either way, people grow and change. That’s life. Just gotta forget about it and move forward. A motherfukker that I used to HATE in middle school ended up getting rich and famous and having a popping music career. That’s just how it goes sometimes.