Did Viacom’s Sumner Redstone have a prenup? Should you get a prenup?

Sumner Redstone, media mogul (he owns majority shares in CBS, MTV Network, Paramount Pictures among other things), and chief executive officer of Viacom, is getting divorced from his teacher wife.
But according to media reports, while the split was amicable, he is only giving her $5 million dollars in settlement money.This seems like a paltry sum in light of what Mr. Redstone’s net worth is bound to be, being that he’s on the Forbes List of Billionaires.
That can only mean one thing. THEY HAVE AN AIR TIGHT PRENUP! That goes to show you how important it is to have a prenup! Learn from Mr. Redstone! Even if you live in New York, New York divorce laws allow you to enforce a valid prenup!
The billionaire octogenarian titan’s wife is a woman named Paula Fortunato who is 40 years his junior. I’m just curious. I wonder what the GROUNDS for divorce were/was?