Probably bots, possibly AI scraping bots.
What helped me immensely were the web crawler reports in admin after being tipped me off on their existence (I had never noticed them before) using this I banned various crawlers. Which dropped anon views. I do think crawlers come in on anon views too. I have no idea how.
The reports also give you b=names of crawlers (user agents) to search up on each crawler to see if it has value.
This topic might also be of use