"Google and Meta collect vast troves of personal information on their users and receive hundreds of thousands of requests every year from governments around the world to access that data"

Nothing stops the big boys to sync all data from all relays and then get deep insights into every Nostr user (and de-anonymize them) as well, right?

Nostr doesn't actually solve the "data ownership" problem. It makes it worse, because there is no delete, what you post here will truly haunt your for the rest of human existence.