Elon Musk is pure and simple egomania. I can imagine him bored in his bed or sitting on the toilet thinking of what to say that can make cryptocurrencies go down.
And wham, he throws out a stupid meme or about 4 words, and that's it. The world eats his story and prices plummet (or go up, if he wants some currency to go up).
Then, he wipes his ass, gets up, puts his phone in his pocket to check it 10 minutes later and see the effects of his tweet.
His ego gets another blast of fresh air and arrogant energy.
So sad. He is becoming a nuisance.