Who knows? The rate of return is so high。
Rich people have resources we usually don't have. They can easily get into something or invest on anything and the legalities are not in their personal name but on holdings they have. There are those who are avoiding the media so they bought Bitcoin secretly. There is a big possibility that Warren is already into Bitcoin and other coins in the market.
Yeah, preservation of principal is key--not losing money--for the super wealthy. WB doesn't invest in anything he can't analyze, so no, I don't think he's bought bitcoin and I don't think he ever will. Plus he tends to put a lot of money into his investments, and he'd end up cornering the market if he bought any. Plus Berkshire Hathaway shareholders would go apeshit.