Before, the show was more of a way to sell toys (not that the Hasbro commercial dep do not use the show to promote toys now, but before things where more exasperate)
about 10 years ago they stopped producing the show altogether. It was only 4 years ago that they restarted.
The current version is attributed to Lauren Faust, a writer and producer that used to play with the actual toys when she was little.
Since she still remembered the old characters she started developing scripts for a new series, reusing characters from the past but also modifying them to avoid CODs and the like
in the end Hasbro actually liked the idea and produced a new show.
this also explains the change of style.
Faust is a fan of Arthurian legends and such, and the team she formed for the show can be defined as a band of cartoon and movie geeks.
no wonder you can now find references to Alien or the Exorcist in MLP...