In general, it seems cosmological theories that encompass more and more of the phenomena of the universe are expected to be more and more mathematically elegant, in conception if not in detail.
Our experience seems to teach that it is a reasonable expectation to assume more fundamental theories will be more "elegant" or "beautiful" than previous theories.
It seems like a similar expectation is what triggered Einstein to reject Quantum Mechanics. We know his experience led him astray. How do we know our experience isn't causing a similar result in our search for a Theory of Everything?
A correllation between "mathematical elegance" and explanatory power would seem to infer that "elegance" is more than just a human construct. How can that be? Why should there be a correllation between what we find pleasing, and how the Universe works?