I thought Skyward Sword would contain plot. In the end, all we can assume is the incarnations of the heros and villans is a never ending cycle, and Demise was so far the earliest incarnation. Maybe there is more to it somewhere in there, like Groose, Zelda, and Link playing the triforce's role, and Demise was another, bigger threat. I can't tell if the followup to Hyrule Warriors either, but meh.