He puts his money and other peoples money into the foundation to manage it. Really rich folks do that. I think his children manage the Foundation. When you ask a truly wealthy person what charity they do... they always answer through their foundation.
He has put very little of his own money into the foundation. Look it up. Over a 20 year period, a man worth $10 billion put a total of $3-4 million into the foundation, and most of the money from the foundation went into other foundations operated by other celebrities.