Investors should optimize for long term growth, yes. The problem is Management (CEO, etc.) will get fired if things look bad. So the incentive for management, if they can get fired, is to ensure monotonic increase. Sometimes — especially for a rocket company! — you should be allowed to fail for a few years. You should be allowed to take big swings, without risk of getting fired. If Elon knows he is in control, he can think long-term. If he's at risk of being let go if things look bleak, his optimization function will be different (and, IMO, net worse for society).

In that case they should stay private

Lol net worse for society. You types can’t stop the blatant propaganda and bullshit price pumping statements can you?