It may be a bit of a grey area ethically since he didn't disclose his ownership until later, but if he was doing it because he really believes in crypto and it's not just a cynical attempt to pump something he's holding and then close the position into the buying frenzy a day later, then I have no problem with it. Of course, though, it's not possible to read this intention from a distance.
One interpretation is that this is in the same ethical category as Instagram influencers who get paid to flash products in front of their users without disclosing that they're being paid.