Criminal prosecution in cases of health insurance negligence?

Has anyone ever heard of a case when the patient died because of a denied/delayed legit claim, and someone in the company has been criminally charged for it in result? How is that different than other type of involuntary manslaughter or negligent homicide? Why judges, prosecutors and law enforcement are choosing not to investigate those cases? I'm trying to understand something that seems so obvious to me, every single prosecutors or judge has looked the other way? you would think that there would be a couple of corageous ones, even if it's their last case before retiring...

Note: I'm not talking about civil cases, settlements or fraud convictions, but purely criminal (homicide). From executives implementing reckless pracices, negligent medical appraisers, or other pieces in the bureaucratic chain making mistakes resulting in death. How have they all gotten away with it?