Don't worry too much, even if he's got 1% of the total supply, he's definitely not the type to dump all of that to get profit and I don't think that he alone can't do it anyway right? There's a board of directors or stakeholders that are going to approve on what's the next move MicroStrategy is going to do so we don't have to worry too much.
The fact that you aren't worried means that a lot of things have gone wrong already. I know it used to be the wishes of Bitcoin enthusiasts for Bitcoin to start getting recognized by the big players like Microstrategy but it has it downsides. Bitcoin was originally created to be an open and distributed network but it won't be if a large chunk of the supply is controlled by big corporations like Microsoft, Grayscale, etc. Even Telsa sold their bitcoin when they felt it was right and caused turbulence in the market.
As more and more big players acquired more bitcoins from the smaller users, they'd drive the price so high that it'd because a rich person thing.