he's probably just investing a small amount, trying to diversify his assets.. it doesn't necessarily mean that he will use his weight to protect bitcoin's development, but maybe it is.
I'm inclined to believe that this is the case much more. After all, his overall personal wealth is well over 5 times the amount of the Bitcoin market cap.
Of course though, he could just quietly buy for a little while, further the already existing infrastructure and end up with even more wealth. Admittedly, that wouldn't be bad at all for the long-term of Bitcoin.