on the other hand the population as a whole has skyrocketed though, and a big part of why people move into cities is because rural areas lose amenities like good public transport.

Yep a lot of the countryside outside of touristic hotspots are kinda dead in France. You can see that they used to support a much more vibrant community but now it's just shut down stores and closed shutters with the occasional remaining locals or implants that were looking for cheap properties. And as others have said replacement by bus lines that are better suited to the low usage.