Why would anyone with that much experience go near Coinbase? Their fees are crazy high for anything you try to do - so maybe it is related to charity - which still leaves the question why choose to lose so much in fees?
Well he may want some cash. If you have as many eth as he has at a cost basis of 25 cents a coin fuck fees fuck taxes.
He may simply cash them and move the cash to a charity.
He likely has 1,000,000 eth coins and is worth more than a billion in cash.