He's not an idiot, the people who praise him as a god and follow his every word and beckon are. Musk is extremely smart, he knows Bitcoin energy consumption is high and unsustainable. And he knows how to manipulate a bunch of people who have no idea what they are investing in/how to invest.

What he did (and this is pure speculation) is a basic pump and dump (well sort of dump, I guess they still have a bunch?). Bought a bunch of Bitcoin, pumped it WAY up, and sold a bunch so TSLA hits revenue targets. A win win for Musk, and it's perfectly legal (versus the other time he tried and got slapped on the wrist by the SEC).

The fact Bitcoin/cryptocurrency drops 365B after someone sends out a tweet is another issue.

It's true markets are highly encouraged by global issues (such as Trump tweets sending stocks high or low) but the fact that Bitcoin went down 15%~ after a single tweet is an issue.

It's way to easy to manipulate it, and that's really bad.