you don't die @ 57 for natural causes.
On the contrary, most people die of natural causes, whatever their age. The only alternatives are accident or murder.
As for the coroner, if he'd died in the hospital, there'd have been no need for an autopsy unless some form of malpractice was suspected.
As for the money, Urbie didn't get the whole $60 million. And since he wasn't one of the "masterminds", he probably didn't get more than $10 million. He was a big spender and had a gambling habit. He also likely spent a bundle on his Clam Lake lodge. So there may not be much left.