Diverging from the ln?

I couldn't help but notice that the ln only has like two volumes and 15 chapters, whereas the manga adaptation is already past vol 3 and chapter 26, and the story – while it low key feels like it could be wrapping up – seems to be going strong.

Are they padding out the content in the chapters to make the manga longer, is it just manga chapters not covering as much as ln chapters, or is the manga diverging from the source material? I'm really curious cause this manga is def one of the top villainess manga releasing rn.

https://anilist.co/manga/109900/Saigo-ni-Hitotsu-dake-One…
https://anilist.co/manga/116799/Saigo-ni-Hitotsu-dake-One…