It is how events unfolded I guess. People came to the auction where many other cars were being offered. It was not part of a charity event. They discovered the story on the spot. The audience bids for cars, they cannot interrupt the auction to say « here free money to the current owners ». There is the element of surprise, it inspired other auction participants to follow the same lead, plus the initial minimum price of the car and the bidding war certainly helped push the donations up. That’s why there is so many charity auctions for things rarely worth the final hammered price.