It is interesting to look at the past predictions on here of AI search/answer companies like Perplexity possibly dethroning Google search and comparing to the reactions of Google just doing the same thing themselves.

Why would it be good if Perplexity does it, but bad if Google does it? What are the principles at play here?

Perplexity does not control who gets traffic on the internet. They don't own a significant percentage of the mobile OS, browse and online search market share. They can't force the industry in one way or the other, consequences be damned.

People don't like Google because it's bad. If competition wins, maybe they'll stop being so bad. But if they become badder themselves, that's not good.