Short version- Early in the pandemic, people in hospitals with covid were being sent to uninfected nursing homes by the NYS health dept. Cuomo signed off on that plan. Covid spread through the nursing homes as would be expected. Protests from loved ones fell on deaf ears until finally the cry was loud enough for the state to relent. Then the cover-ups began- hidden evidence, burned documents, but the bodies of 15,000 elderly victims were hard to hide, and all signatures led back to Cuomo.
His sex assault accusations followed, and the Granny Murders, although having enough evidence to prosecute, were mumbled and bumbled by the state and let slip into the public memory hole, while Cuomo quit Albany to parts unknown.
He handed over power and prosecution disappeared; that's how it rolls in NY.
The details are out there and worth a look if you enjoy true crime stories.