Unless Twitter is paying the Tesla for Tesla’s employees time to Tesla, whether you care or not, doesn’t matter. A part time CEO of a public company is using the public company’s resources on one of his private project. If I owned a business with someone and found out the other owner was using our company’s funds but told our employees to go mow his house’s lawn, I would consider that misappropriation, embezzlement even. We don’t know the details here but I would hope it’s above board.