One thing I wondered was why the writers (Gilbert Ralston and Gene Coon) chose Apollo as the last surviving god—why not Zeus, king of Mount Olympus? Apollo was god of music and medicine, primarily -- less powerful than other male gods like Poseidon, Cronus, Hades, Ares, Hephaestus, etc.
Unless the writers were slyly alluding to the Apollo space program that started in 1963…to tie in with the “ancient astronaut” theory that space travelers visited earth eons ago and were perceived as gods.
Apollo was a second-generation god and half (Terran) human. The implication is he disagreed with the decisions of the elder/pure gods. It was only in the end that he realized they "were right".