I've heard of the theory that the Thalmor's motivations for the Great War and Skyrim's civil war were part of a larger goal to unmake Talos, mankind, and Mundus. Is there an objective version of this theory? I know that much of the source material for this theory comes from developer commentaries that aren't in the game, but is there anything in the game or previous games that support it?

The most concrete game evidence comes from the books like the Monomyth and Varieties of Faith that describe Aldmeri religious ideals and their opinions of Mundus, but there is some slight dialogue evidence. Ancano claims he could use the Eye of Magnus to unmake the entire world.