In my recollection, the 420 tweet was precipitated by a hostile takeover bid from Sudi, which Elon wanted to avoid. (They went into another EV co later.) Probably he had some oral agreement/understanding with e.g. VW for funding, or some of the wealthy guys in his buddy-circle.Curve ball (total devil's advocate here), but what if he doesn't sell and it's a bear trap to expose unethical or illegal trading? Recall the 420 tweet but never did go private - for reasons beyond me but likely to protect the shareholders or mission or both. So what if a similar event just happened, he didn't sell yet, and reexamines to find that it's not advised. In other words, wall street did something unexpected, he's reconsidering? Or a bear trap which I'd rather believe. Or just nothing and it's done, who really knows. This story is not over, something tells me. It's quite the movie segment in fact.
BUT, he wanted to protect The Little Guy (TM) investors and found out a bit too late that many of them were not allowed to buy into a private enterprise; likewise many smalltime investors' funds. And that was his reason to back out. 420 was simply the conventional 20% bonus on that day's share price.
Not a great mystery, really. IMO. Of course bears and other vermin pounced ruthlessly. Well, they got pounced back pretty thoroughly since! Every single shorter remaining as of a few weeks ago is far under water. Best place for bottom feeders, right?