It might be as simple as the public perception of Elon Musk. Before he bought Twitter, many of us thought he was a very smart engineer who could also be an asshole (the two are not exclusionary). Now that he's running Twit (or, as he claims, his dog is) there's been a good bit of re-evaluating "very smart". (The "could be an asshole" part, not so much.) He'd do Tesla stock a favor by resigning from that board - and not 'pretend' resigning, like at Twit.