Moral hazard?
Second, the money was used to fight polio, a terrible disease. Moral hazard would be Nigerians driving Ferraris purchased by Melinda and Bill. This is not that.
If the Gates want to eliminate such diseases, they must be elated to see effective programs spending their money to do it.
The Nigerian kleptocrats have effectively externalized their healthcare costs so that they can buy their Ferraris or more likely a fleet of pimped out G-wagens.