Huh? This doesn't have anything to do with Cuomo. This is the New York County (Manhattan) DA, who is himself an elected official.
The New York State political machine is incredibly corrupt and interconnected. And Cuomo himself is more powerful and influential at all levels of state government (which includes country-level positions) than any governor since, well, his father. It's really not unreasonable to suspect he had a hand in this.
What Cuomo wants, Cuomo gets.