I recently released a book using Kindle Unlimited Publishing and was surprised at how easy and simple the whole process was. Especially the Kindle only bits since the formatting and dimensions of the cover don't really matter for digital versions.
It was quite the learning process to get the physical books right but that's a different story and one that bots would probably care much less about since the margins are so low.
However, even outside of nonsense written by AI, there were already a ton of questionably written titles that were trying to take advantage of SEO and keywords. This feels like an easy next step for the people who never cared about writing interesting stories and just saw a system they could exploit.