JFK, LGA, EWR airports are extremely busy with airliner traffic. Tetorboro, White Plains and god knows what else GA-wise, only add to a barely manageable workload for ATC in the greater New York control area.
The approach corridors over the city are uber-crowded with a precarious mix of heavy jets arriving from all parts of the planet, and green, well-moneyed weekend hobby pilots.
I’m only surprised this didn’t happen sooner.