Assuming for a second Optimus is not complete vaporware, and that people will trust Musk with humanoid robots in their home after he said "I'm not building a robot army unless I have control"....

Optimus will face the Roomba problem. Cheaper robots from competitors will destroy any profit margins, and there's zero moat.

And the problem with shorting Tesla has been apparent for years: the market can stay irrational longer than you can stay solvent.