The guy is probably just trolling. He enjoys weird things make weird jokes and so on. But despite that tho, I am still one of his biggest fans. Because behind those weird jokes and personality he shows, is an amazingly brilliant and innovative mind. But yeah, back to topic, it may only be just tweeting for fun and others took it seriously which is why the price of dogecoin increased that much.
I don't think this is a joke things, he might have been paid to do this, I know he is filthy rich but this act is something outrageous, I can possibly say that the first one he did on bitcoin could let him know he is already a crypto influencer and celebrity which his reaction to anything related to cryptocurrency will affect the market one way or the other, that reputation alone should let him behave mature and stop manipulating the market.
Additionally, if he keeps on repeating this act, he might be a tool where whales pay to manipulate market for their own favour by simply buying low and contact him to pump by signifying some little interest, who knows..