Superconductivity is fascinating. I don't know how people were able to come up with the explanations. Crudely, the reduced temperature means less jiggling of the metal lattice. This in turn makes it possible for the nuclei to be pushed around by electrons to form essentially sound waves (phonons) in the lattice (think of the lattice compressing and expanding due to interplay with electrons). At a certain temperature and therefore a certain frequency of lattice oscillation, electrons pair up to form "Cooper pairs" - they move in concert due to the lattice movement. What's crazy is that cooper pairs become a sort of pseudoparticle, and their quantum behaviour is different to regular electrons. Cooper pairs have integer spin (as opposed to half-integer spin), so they no longer obey the Pauli exclusion principle and all the electrons in the entire material basically form one giant condensate that extends through the whole material and can all occupy the same lowest energy quantum state.