Bitcoin is pretty much explicitly designed to use as much electricity as the market will allow, without becoming any more useful. If you removed 99% of the miners from the current system, Bitcoin will still be exactly the same - it won't be any faster or slower, and the same number of transactions will flow through. The cost of electricity serves only as a lower bound on the expected value of a coin.
Neural nets on the other hand generally show more capability as you add more compute power. There's a point where it's less valuable than the cost increase, so people don't do more than that, but it isn't constant value like Bitcoin.
It wouldn’t be exactly the same, because if you had all that mining capacity and 99% magically took a holiday, there is now enough mining power to take over the network anytime. It’s not secure.
Same with AI. Now that the Mythos and other models are finding exploits in every code base and anyone can run them, you can’t afford anymore not to keep burning credits securing your code base. It’s like proof of work red queen theory. You have to run faster and faster just to stay in place. Great business model.