For those who have gone stir crazy over the lore (because the timeline and canonicity of any one games dialogue) or are just too young:
Ganon was already a beast. His pig-like form is the form of the Moblins that follow him. He created a drow-warrior form in OoT, just as he created a Shadow Link in ZELDA II and Aganon (however it is spelled, from the SNES game.) Ahganim or whatever was considered a separate sorcerer but when I was a child I assumed HE was just the 'Link's Awakening's Ganon.'
--Up to that point every game had a diff spelling:
-Ganon
-Gannon
It was revealed that like Ganon's Phantom Form (in later games), Aganhim was only there to do Ganon's bidding while he was away.
ONE TIME Ganon came back as a Drow. Since OoT was SO popular (deservingly so) NOW Ganondorf has become the character and Ganon has become "Beast Form Ganondorf."
Dorf was added because he's desert drow now. He's still just Ganon. This wouldn't have happened if Nintendo had stopped using the Dorf motif repeatedly, or at least gave Ganon a new Ganon( ) every sequel.
That's... not even remotely how it works.