Let's say you donated to Best Buddies because you believe in their cause. You see Tom Brady there and he's volunteering his time (and probably writing it off on taxes somehow) and he convinces you that they got a great cause helping people with disabilities so you donate 50,000. After say 20 mil is raised they his Toms non profit (that had no real stated goals but fundraising for good causes Brady chooses) with 2-3 mil. Tom then decides the ritzy school his kids go to (or want to go to) can use a new library. He doesn't pay for that out of his money. He takes the money Best Buddies gave to his organization (that people gave to an organization to help disabled people) and donates that money instead (while probably writing it off on his taxes somehow again).
So now Brady looks like this great guy. On the surface it looks like he is do charity work to help disabled people, and donating to organizations in his community (or that serve his family). However, he hasn't paid a penny. In fact he took money away from disabled people, to make it look like he did good. Even if the organization had paid him for his services. He would of been taxed for it, so on top of that this is letting him avoid paying taxes.
With all that said tons of celebrities do this. A few actually cause about a causebbut the majority use these tax exempt organizations for shady things like this.

It's the American way