The parent article does a good job at explaining the whys and hows.
For the stations that where actually open at some point, it was mainly a matter of optimization: new hubs being built, profitability, etc. The end of WWII has been the turning point for most them.
Porte des Lilas was a prototype station repurposed for shooting movies in a controlled environment.
Haxo was part of a failed project to connect two lines. It was never officially opened so we, locals, don't really consider it as a station.
The buff between Place d'Italie and Corvisart has never been a station. It's more of a curiosity than anything.
Not mentioned in the article are the former end-station of line 5 at Gare du Nord, now a training ground for metro drivers, Arsenal on line 5, Porte Maillot on line 1, and Molitor, which was never even connected to the surface.
I am not sure how popular the ghost stations of the métro, the prohibited sections of the catacombs, and the "petite ceinture" are with today's teens but they made Paris a gigantic interconnected playground back in the 80s/90s.