I reckon Elon Musk simply has too much on his plate with Tesla, SpaceX, Bitcoin and the media.

He obviously needs to blow off steam, and his joking around with Dogecoin shows that. Even though it's a bit hypocritical as Dogecoin is energy intensive.

He can't go on living at 1000mph for ever, so he will have to slow down and relax and hopefully stop throwing his opinions around for fun.