This is true, but I feel like you're trying to draw an inference here that doesn't really work. You're unlikely to be worth $9 billion through a love of hamburgers, but that doesn't mean somebody worth $9 billion is unlikely to enjoy hamburgers either.
I was cynically implying lavishly successful business people are often shrewd, calculating, and clever insomuch as any generous gift is likely also a form of investment
What if you start out at say 50B and donate a 41B away to charity to help address huge challenges facing humanity - call it something hokey like "the giving pledge" - and end up at 9B?
Definitely possible, but like the parent poster mentioned, unlikely.
Far more people have intentionally built their way to $9B than have intentionally reduced their fortune to $9B.