In 2020, as I understand it, Bill gates sold less than 1% of MSFT on the open market there: his holding went from a bit over 2% to a bit over 1%. He had been steadily selling over the last two decades.
Contrast that with Jeff Bezos, who owns 10% of Amazon, or Elon Musk who owns over 20% of Tesla. Half of Gates's holding is nothing in comparison to half of Bezos's.
When you sell large share blocks like Gates did, you do it very slowly to avoid market impact. Elon Musk couldn't sell slowly enough to avoid an impact when he sold shares to buy Twitter.
