It's not "he's rich". It's that he has been actively engaged with all the research programs that he's funded. Global health philanthropy has been his primary job for over a decade. When you're working with experts in the field for that long, you do learn a thing or two.
Seriously, you're picking the wrong argument here.
Now, if Gates had started talking about rainforest conservation efforts in South America (random topic), he'd have little authority. But on this specific topic, he does.
Loads of people have been engaged with the programs Bill Gates has funded, including a great many doctors. Bill Gates doesn't have some unique level of experience dealing with organizations addressing these matters, and a great many people dealing with these organizations seem to have more expertise in the matter than Bill Gates.
> Global health philanthropy has been his primary job for over a decade
Key word there being philanthropy, e.g. he's rich. Instead of listening to the guy with the wallet, we'd be better off listening to the people who actually put Bill Gates' money to use with their actual expertise in matters other than being rich.
Seriously, you're picking the wrong argument here.
Now, if Gates had started talking about rainforest conservation efforts in South America (random topic), he'd have little authority. But on this specific topic, he does.