"Now MicroStrategy holds about 138,955 bitcoins" - That's a lot of Btc lol
Having such control over the supply might not be the healthiest thing for the industry. Imagine if he decides to sell 10% of the supply owned, it might have a huge impact on the market - especially if there's no deep liquidity to absorb the selling pressure. On the other hand, he is free to do whatever he wants, that's the beauty of capitalism and private property.
Fun times ahead.
Selling 10% wouldn’t do anything really. Even selling all would hurt bitcoin in long term, maybe only short term price decline. However, the fact the decided to sell could cause panic and make others sell as well. That probably would create long bear market, similar to what happened in 2018 when MtGox trustee sold significant amounts of bitcoin and announced afterwards that they may sell more.