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.
You are right, however in my opinion the amount of his investment is not as important, as the information for wider public that goes beneath - another successful enterpreneur thinks that Bitcoin is here to stay - in the aspect of good publicity it's priceless.
This is the correct way to look at it. General public always takes inspiration from established players to invest their hard-earned money. If some bear hears about popular investors investing in Bitcoin, he would be less reluctant to invest his own assets.