He doesn’t hold dollars, he mostly holds equity. Also it doesn’t seem like he’s directly involved in the day to day tasks assigned to delivery drivers so it’s weird to assign blame to him for that as well.
One could argue that if drivers were unhappy with the work, they could just quit. Another would argue that that’s a callous way to view the problem as a new job may not be easy to get.
I’d link these 2 issues and say my view is that if Bezos were to sell his stock to give to charity, Amazon’s own stock would plummet which would indirectly force the decision to leave Amazon onto their drivers. A depreciating stock price means their corporate RSU grants look less attractive, which I speculate would make working at Amazon less attractive, leading to worse talent and declining company performance. If a decline was to happen in this way there would probably be more demands on drivers, potentially decreasing demand for the job as the whole, and leaving the drivers who stay behind in worse conditions.