According to the article it sounds like it was a private transaction. Not over the exchanges/open market. I presume the buyers and sellers were both sophisticated enough to understand the transaction and negotiated a price. If the seller dumped them all in the open market it would have negatively impacted the share price so I presume the buyer knew that and negotiated a price that incorporated that fact into the purchase price.
Looks like next week is in for a wild ride with tens of billions moving around.