nostr unlike the others mentioned as "social protocols" is that on a pure technical basis nostr is a superset. It isn't restricted as a social protocol like bluesky or mastodon is.
Facebook could if they want incorporate the nostr protocols, set their systems to only use facebook servers as relays.
All the Facebook vibe would stay, their system would run on nostr. And we outside of that bubble wouldn't notice a thing: Unless they open the system.
But it would be cool tech as through the nostr protocol they could give their users more direct ownership of their data.
I see it as a user distributed database system, when I program in it. And like using it even when not doing social apps.