Cyclic history – and specifically, the notion that empires will inevitably rise to galaxy-spanning heights, then decline not to mediocrity or middling-power status but to utter oblivion – is deeply embedded in the DNA of science fiction. Asimov did it in the Foundation series, of course, but you see it everywhere in space opera: the backstory of Niven & Pournelle’s The Mote In God’s Eye, Poul Anderson’s Flandry series, any number of David Weber novels, the Traveller tabletop RPG, the Tough Guide to the Known Galaxy (http://www.rocketpunk-observatory.com/spaceguideF-L.htm)…
Yet, to the best of my knowledge, it has nothing like the same prominence in fantasy. Why’s that?