I’ve heard the theory that it’s LLM-generated spam content ruining the remaining results. There’s presumably just so many webpages with heaps of garbage text now, that search engines need to aggressively filter anything that looks remotely like spam, including lots of legitimate content.
I do find it kind of terrifying, too. It’s happened a few times now that I remember some event from a year ago or so, sometimes even being relatively certain what the title of an article was, and I just can’t find anything about it. As if it had never happened.