He has a "secret" LLC where he is dumping BTC. He used his company to pump his BTC where he could dump.

Microstrategy's executives also mass sell stock prior to them announcing BTC buys.

Basically, Saylor and executives are raiding Microstrategy. Everyone knows that company is dying hence why it is now an unofficial "trading" firm / index for BTC when it's supposed to be a tech product company.