5 billion is massive. So much of that 40bn daily volume is just leverage. Sort of like the derivatives market, trillions of dollars in volume but nobody has that much money, it is just margin. So even if some trading firm losses 1-2 billion everyone panics and goes out of the market. It actually happened during the flash crash.

Also, I highly doubt they sold those 5bn of shares in any exchange. Most likely they did it over several weeks on a dark pool. Because again 5bn is massive and it would cause a crash in any open exchange.