Why would you think “rich people made money”? They already hold the shares and would be trying to sell. It would be impossible to sell any large amount of shares after hours directly after a huge negative issue. If you could sell (say $1 million worth), it would be at a much lower price.
That’s probably why the price dropped. The market doesn’t actually react to news, it reacts to investors buying and selling. If the price went down that means people with lots of shares are trying to get out.