The shorts against Tesla were enormous. Millions (billions?) were put against Tesla. You can't tell me that the shorters did not invest extra money to make their short profitable. That extra money would go into PR to make Tesla look like failing company. That is not fair play either... Basically Musk gave a punch back after being bullied and stressed.
Self-defense?
Also the Tweet started with: "I am thinking of". Not matter of fact, but just announcing what you are thinking of.
Anyway... maybe he can be CEO by proxy or focus more on leading the engineers.