1. About his work at Microsoft
2. Or some conspiracy theory about world domination, population control etc
I'd be interested to read more on how societies he's directly worked with think of him, if you have any links
3 : he wants to use his money for philanthropic cause. I can't overstate how great it is. The way he uses his money though, has been pretty controversial. From pushing a pro patent agenda in countries that are too poor to afford medicine made under that system to accusations of straight up using his money so his ideas are applied, even when they go against actual experts with data (and actual expertise) to back their positions.
For the lazy, there was a recent video on the topic : https://www.youtube.com/watch?v=P-fqcFaZKHQ
He had this huge presentation about a laser zapping mosquitoes. The patent was fed to a patent troll, the whole board was stacked with his friends, the company produced nothing and was set up to sue anyone who did try and produce anything. 10 years later they still haven't produced more than the one prototype. The 'charitable' donations were literally just tax write offs that paid for his friends salary.
Since then I really don't take him seriously at all. His charities are just a way to reduce his tax bill and look like he cares, while he's just paying his friends to work on projects they find interesting regardless of the chance of success.
In short: hubris, corruption, white collar rico and tax evasion.
It'd be like saying it's a conflict of interest to promote access to clean water, while also investing in companies that supply clean water. Sure. It's a conflict. It's also exactly what you would do if you just wanted people to have clean water.
If I were in his shoes I'd focus more on issues like education, improving basic utilities in urban areas, fighting corruption and enabling economies to expand.