Loitering in a public park known for illicit activity at odd hours is going to attract the attention of law enforcement. That he was driving on a suspended license raised even further suspicion that this was not your typical law abiding citizen. I’m no great fan of police in the modern era, they’ve gotten paramilitarized and often enter into any interaction with an adversarial mindset from the very outset. But, keeping an eye on potential hotspots for illegal activity and questioning the presence of suspicious individuals is in my opinion a legitimate function of law enforcement.
Wearing a winter coat & NO shirt causes more suspicion.