If you have more money than anyone else on earth, the highest leverage use of that money is going to be to fund projects that require more capital than anyone else can afford to fund and that governments are unwilling to fund. That way you know you are actually adding to the opportunity set and not just displacing someone else. The difficult part is, of course, deciding which of those projects that only you can fund will actually be a good bet, but that doesn't change the fundamental calculation. Not sure if that's Gates' strategy, but it would make sense if it was.