You can search for an old kind-3 contact list event and recover the full npubs list. I don't know if there are clients that let you mass import them, but with a console tool should be quite easy to do.
Discussion
Excellent, I'll check that out! For some reason https://www.nostr.directory/ is also broken to add followers from Twitter. It lists them but doesn't update, even if I just add one at a time.
https://www.nostr.guru/p/fe1d10131ca6103715d261f1615a8cd31f6b68a3d1a3272aab8e9e83f787126e
Here I can see only the today contact list.
I tried to query relay.damus.io and nostr.wine but I can get only this last contact list, perhaps they have a time limit; you could ask some relay owner for a backup.
If can be useful this is the REQ filter to use:
{"kinds": [3], "authors": ["fe1d10131ca6103715d261f1615a8cd31f6b68a3d1a3272aab8e9e83f787126e"], "since": 1672569529}