If you're giving away so many billion, you might as well oversee yourself how they are going to be spent. What sketchiness do you see here? It was already his money.
Non-profits are regulated so it's transparent what they do with the money other people give them. In this case, it's Mark's own money. Even if he executed the sketchiest imaginable scheme, he's only wasting his own money. He is free to start a commercial company with it instead, but he decided the goal should be to do some good.
The time this will become a problem is the second the company accepts money from other people. Then I will join in picking up pitchforks.
