As a billionaire, why commit insider trading for a few hundred grand in profit?
There is a (small) possibility that he really didn't know (the second part of the complaint), but decided it's not worth a fight with the SEC cause it's such a small amount to him (and he has no interest in serving as an officer of a public company in the next few years anyway).
Though, the version others have said is still more probable: Reach people wanna get more rich, no matter the method.
Well, at least it did.
Invest everything you have into a company that put batteries into a kit car.