4chan has always been huge and relatively mainstream among internet users. "Anonymous" as a hacking collective has been active and in the news at least as far back as 2007. It's a combination of the same stale thread topics being the only regular activity or pushing fresh activity off, American politics largely being pushed by mainly right-wing and Russian troll farms, captchas making posting take enough effort that some people don't bother, selectively moderating against other threads but not logfag, and leaks revealing that even though 4chan isn't the honeypot we thought it was that they do store tons of info on users.

I think the two easiest, directly changeable (i.e. not an internet culture issue or dealing with outside forces like the troll farms) way to help things is just better moderation (start deleting logposting), and increase the amount of threads that can be active, including how many posts they can contain. You can't have fresh content if the regular threads and logposting pushes it out too quickly, and that's exacerbated by how quickly the regular threads reach EOL and need a new thread to be made.