Idk. Toei is definitely more interested in the money they can make (as they should) from the series because no company can survive or even needs to invest in a failed project.
It's most likely a money issue, which may be a reason they had partnerships with Deen (maybe).
There is a contract between Toei and Naoko's publisher, etc so it's more probably like creative difficulties.
Sailor Moon certainly isn't Toei's highest earning franchise but it earns enough to keep it relevant I suppose.
I find it interesting that despite the show saying it would stay faithful to the manga, some of the shock horror in the manga was toned down and has been since Crysternal came into existence.