[gaugefield]

One of his earliest great works is one that indicated wrong in the foundational aspect of the theory, namely incompatibility with E&M Maxwell equations and Galilean Transformations and E&M equations not being invariant under those transformations. The principle of symmetry is one of the foundation issues in physics. He also had th wisdom of understanding of the physics of new transformation, Lorentz transformation, which we know today as Special Relativity.

Yes, of course he was well-trained and had the enough background, but also the problem at the time was the type of problem that was solvable (i.e. no limitation in terms of tech) and that required new framework with new understanding.