It's difficult to know exactly why Elon does what he does, but he probably has access to sources of information that we may not, that may reflect unbiased reality a little more accurately. IMO Elon thought it would make money, simple as that. Occam's razor and all. I think later he realized it doesn't alight with Tesla's mission statement because of all the coal used to support it. I think he does some things on impulse, this is believable given some of his bizarre tweets and interviews.
If you think btc energy useage isn't an issue, IDK what to say, all you have to do is look at the mining requirements and it's obvious. It was obvious 10 years ago when people were selling btc mining hardware that costs hundreds of dollars a month to run, and the requirements increase with time so btc uses more and more energy. This is undeniable even by the most hardcore btc-lovers. Those making excuses for this are showing bias that is distorting perceptions to the point they have little to do with reality. I would argue perceptions of btc are massively altered by purchasing btc, to a disturbing degree.
While current financial institutions use a lot of energy, it's NOWHERE CLOSE to btc useage and the services they offer only overlap to a degree with btc. Most of their services will still be required in some form, the false equivalence between btc and CC companies is ridiculous and nowhere close to reality.
Whatever your thoughts on Elon... personally I disagree with him on most things, Tesla cars suck and are not green, going to Mars is a stupid goal right now, the Cyber Truck is ugly AF, etc... it's hard to ignore his massive success and the influence he has in the world today. It's possible he just knows more than you do and is smarter than you are. Just saying... Oh, and Doge is going to $5.