Not being public makes Twitter less valuable as a product, though; for all the noise about people still using it, some influential people are not, and others are now dual or multiposting on Twitter and one or more of Threads, Bluesky or Mastodon. Now, some of them are doing that out of disgust with/distrust of Musk, or due to its increasing problems with scam ads and unmoderated propaganda and similar, but some are doing it for visibility/shareability.

Twitter traditionally had far more casual passive consumers (who saw tweets only via links) than active users, and those consumers were important to certain high-profile posters.

what does that have to do with anything? they can still show ads to non logged in users.