Has he really? a) it's really obvious that he's doing it — I cannot believe he hasn't fallen foul of regulators yet b) he hasn't gained anything from this particular deal yet, as far as I can tell
Unfortunately, he didn't expect Tsla to go down so much. So now, on paper at least, he has lost more on this deal than he gained. Call it a little bit of Karma.
It doesn't matter how tiny. 9 billion in stock market trade by management will move the market both from the amount of sell orders and from the market reaction.