We can't know for sure if Mr. Buffett doubles the game all the time, but I’m personally more inclined to think he wouldn’t have dealt with such things in the old days - because if something like that were revealed, he would be labeled a liar. The question is how much does a man hold on to his reputation, and it seems to me that he would not sell it for a few billion $.
Well bitcoin provides a very unique utility which is to let people park some amount of money in a place where nobody could know or touch (unlike fiat in the banks). Rich people have always been looking for such opportunities and diversifying into bitcoin is a strong possibility.
Who cares about reputation when money and financial sovereignty is involved?