SoftBank unmasked as ‘Nasdaq whale’ that stoked tech rally
This is market manipulation.It is an example of pump and dump: a market participant creates a position for the purpose of inducing other participants to join them before selling once the price moves in the direction of their position.  What makes it unusual is both the size and time scale of the manipulation.Typical examples of this are seen in illiquid stocks for a few thousand USD at a time, with time ranges from hours to days.It is frowned upon by regulators because it increases volatility in the markets that are disconnected from fundamentals.