well i think they are, there is a rumor that Zuckerberg is investing in bitcoin. And hell yeah they know that it exist.
I also think of the same thing. Bitcoin is a good investment. Evwn if they are already rich, ofcourse they won't be satisfied with that. But maybe, they are investing into ICOs or projects because the profit is bigger. The higher their investment and the bigger the project is, will affevt the returns that they will get especially if their investment is a success.