Besides, billionaires don't always make the right decisions.
Let's talk about the time that Warren Buffet bought about 129 million oz of silver at $3.50 to $4/oz. around 2002-2003. Then he dumped all the silver in 2005 around $6/oz. Good timing on a great trade, right?
By 2007 silver was up to $17/oz.
By 2011 silver was up to $48/oz.
Yeah, what a loser, only made 260 million buckos. And it took a whole two! years! That is, like, a LONG time.
Don't get me started on his amazingly bad long position he took on IBM (about 10 years too late), where he ended up losing $444 million.
I doubt any of these billionaires have problems obtaining enough to eat.

Unless they are stricken by some kind of eating disorder. Even in the event of total financial collapse; I'm sure they have enough assets to barter to keep themselves well fed.
Warren Buffett eats the $1 menu at McDonalds every single day for breakfast. He is going to kill himself early eating that shit.
https://www.cnbc.com/2017/01/30/warren-buffetts-breakfast-never-costs-more-than-317.html