I recall brony ment a term for the fans of the show but then it evolved into meaning: The people who go crazy over the show, and the average fans split off.
Originally, the word was used to define male-fans.
It went from that to defining any fan of the show.
Some find it to be a prideful title, some use it to that extent as well, so many may think the word defines the more
'interesting'-fans.
This turns the less-'interesting' fans away from the title, so they drop it or simply say they are just "fans".