Hmm...According to Zelda (again, according to Zelda wiki), Twinrova tried to use Zelda as a perfect sacrifice to free ganon from whatever realm, but thanks to link, Twinrova desperately sacrificed herself to revive ganon. Unlike Zelda, Twinrova was inpure, so instead of resurrecting Ganon, they made an insane monster (either that, or an insane Ganon). When Link Defeated him, Ganon regained his Sanity (partially at least) before being destroyed/sent back to his prison realm.
Anyone want to speculate on the original game? It may be the most mysterious title in the series, seeing as how it's based in a portion of the Hyrule that was explorable in its sequel, Adventure of Link, but even then, it's completely geographically different than the Hyrule that we all know and love. If somehow it is the same Hyrule, given that it has both Death Mountain and the Lost Woods, why has Ganon taken over Death Mountain? The Gorons are assumably gone or dead (likely by the will of Ganon), the Zora are no where to be found, and all is different. Of course, it's an incredibly primitive game in comparison to the modern Zelda games, being based around hardly a story at all, but rather from point a to b to c all the way to the end of the game. While it wasn't linear, it still was.
It's really difficult to talk about the game, because most things said will probably be opinion based as the game does not have much to offer at all conceptually.