The obvious difference is that AI has abundant use-cases, while Crypto only has tenuous ones.
Maybe there is added negativity considering it is a technology where there is clearly a potential threat to jobs on a personal level (e.g. lift operators were very negative towards automatic lifts).
Subjectively, the two flavors of AI-negative sentiment I've seen most commonly on HN are (1) its potential to invade privacy, and (2) its potential to displace workers, including workers in tech.
I think that (1) was by far the most common concern up until around the ChatGPT release, at which point (2) became a major concern for many HN readers.