(Honestly, this looks like a bug.)
But assume that's a real bid wall:
I have bad news for him.
There will only be 21,000,000 BTC, ever.
There are only 10,600,000 BTC available right now if he bought every last one.
There's no way he'll be able to buy them all for $84.
But assuming we all went totally insane and everyone sold him 10,600,000 BTC at $84,
He would spend $890,400,000 and have $1,399,999,109,600,000 left over with which to buy:
All the world's GDP: $69,970,000,000 (we could all just receive a paycheck from him for a year and do nothing)
All the US's real estate: $25,000,000,000
(I want to add in the cost of real estate worldwide but there aren't good figures on it, so please just skip this plot hole, thanks!)
Unfortunately, at that point he would own the entire world and would have to burn the rest of his $1,399,904,139,600,000 in one giant bonfire, because nobody would have any goods, property, or services to sell him so the USD would be worthless.
Of course, BTC prices would skyrocket. BUY BUY BUY!