It'd be funny if Disney got lazy enough to say something like, "The backstory of how Anna and Elsa got into this park is based upon the popularity of one of the songs from the movie which drove IP awareness to the point where everyone was asking, "Where's Elsa and Anna??" This led us to "re-imagine" a ride based upon Norse Gods, trolls, polar bears, puffins, oil rigs, and a little shanty town and making into the magical IP-based attraction, which is going to have a positive return on gate receipts, that it is today!"
(not all that far off from having to trot out Rhode for Pandora's explanation - or Dinoland's explanation)
I swear they could put some old, mechanically questionable carnival rides into their parks and tell people, "This is the story of an abandoned carnival..." and Disney people would eat it up! "Oh, it's SO authentic! It's like I'm actually inside an abandon carnival! Look at the detail - most of the lights are out on the rides - just like the parking-lot carnival I remember in front of the Safeway when I was a kid! There's just so much detail! That's REAL asphalt!"