is there a human behind such decisions or is it just an automated algorithm?

Doesn’t sound like retaliation to me, it sounds like their scheduled web crawlers are finding that content they used to index is now no longer viewable and this removed from search results. Pretty standard. My guess is that there were 400 million URLs listed and as the crawler uncovers that they are no longer available, that number will keep dropping to reflect only content publicly viewable. If only 500 URLs are now publicly viewable (without logins) then that’s what they will index. Google isn’t a search engine for private companies (unless you pay for the service) they are a public search engine so they make an effort to ensure that only public information is indexed. Some folk game the system (like the old expertsexchange.com) but sooner or later google drops the hammer.

Maybe they could allow some of the text to show in order for spiders to index the tweets correctly, something like the first 280 characters could work.

Not entirely related, but I wonder how things like Lemmy/mastodon/other fediverse things compare to Reddit/twitter in terms of search engine indexing. Would posts like this even be indexed? Since posts are accessible through many instances would it be indexed multiple times? Would this affect ranking?

I am genuinely curious. What's the role of the new CEO if this turd keeps doing everything he can to burn this ish to the ground?

Queue the person on the forums telling you that it’s your fault and not the search engine because somehow you’re doing it wrong.