Bitcoin is an environmental disaster. How/when can it be stopped?

Your premise is false. It's not an environmental disaster. If you think it is, point to the harm. Then explain why video games or Netflix or whatever are not bigger "disasters".

People buy electricity and do what they want with it. It's not your business. I don't come into your house and check how much ketchup you're using on your fries. Please sort out your own life before going and being a neo-climate-alarmist-electricity-use-hating Baptist about how other people are living theirs.

Regardless of the motivation, i find the question of how would one stop bitcoin rather interesting.

I have not put a lot of thought into it, but my attack vector would be to force a government crack down.

To achieve this in china, where anecdotally most of the miners are operated, one would essentially have to make bitcoin an effective bypass around the party's censorship. Just posting a few bits of illegal content would of course not be enough, there would have to be an entire ecosystem of apps allowing you to read data of the blockchain and then a concerted effort to continuously upload content, think the nytimes uploading their front page in chinese daily. As you can imagine that would be rather costly.

Another potential attack vector that seems cheaper (but maybe isn't) would be to find/inject software vulnerabilities that would allow the attacker to cause service disruption or data loss in the most popular clients. Remote code execution, allowing one to take control of the nodes would be preferable as any flaw that would just cause a denial of service would be easily rolled back.

Read up some theory on Bitcoin, especially about difficulty.

I will fight any efforts spurred by baseless claims about Bitcoin environmental impact.

It simply needs to not be profitable. As long as it remains profitable, either by artificial inflation or actual demand, its here to stay.

Were awfully selfish creatures, aren't we?