Eventually he either realized or had it pointed out that the environmental controversy would be problematic for an electric vehicle company.

Any Mathcoin (or any trade) is an exchange based on energy spent (not including Mathcoins insane transaction cost). It's an abstraction from someone mining for materiel from the ground and trading. An energy cost is involved.

What's the killer use case? I can just as easily purchase wine, art, or goods which appreciate and will indefinitely hold a non zero value, even if civilisation comes to a halt, someone wealthier than me will want to get drunk.

If the use case is a fungible, I'm good. If I want to do illegal stuff, I can just as easily launder those goods the same way.

p.s. if you buy expensive wine in restaurants, thanks.

Are you saying AGIs will earn a living by operating a cryptocurrency mine?