Unless they held majority of the protocol traffic.
That's why Google has so much power. If they want something to vanish from the internet they can just filter it out from their search results.
Same applies to btc and nostr.
If for ex. Amethyst and Damus would agree to filter out certain event types or event payloads those notes would be wiped out for majority of the users.
That's why community needs and should react on attempts of censorship.