For Goblin world, Peter was very intent to make it something other than just a black hole in the ground with creepy goblins scuttling about. That’s were the idea of having everything jerry-rigged out on these platforms appeared, creating a really much more interesting universe than something at the bottom of a cave. And we just went on in that light.
I think the only thing worse than that insane decision was the idea of giving Thorin Oakenshield an extra nemesis. "OK, he's got his own internal battle pitting pride, greed and honour against each other, check, got a the biggest baddest creature in Middle Earth to fight, check, there's the Necromancer lurking in Dol Guldur of course, and then there's the journey itself... I think we need a more cartoonish creature for him to fight, that totally rewrites the story line that Tolkien gave us, don't you? Isn't the troll sequence a little too grown up for our target audience? How about a GIANT WHITE ORC!"
Sad to see such a great talent used by Jackson to make such a indefensibly bad Hobbit adaptation. The LotR trilogy, for all its shortcomings, was a much better effort.
"This is the one they'll remember me for," Ed Wood, speaking of Plan 9 From Outer Space