The spread of Greek literature, mythology and philosophy offered Roman poets and antiquarians a model for the interpretation of Rome's festivals and rituals, and the embellishment of its mythology. Ennius translated the work of Graeco-Sicilian Euhemerus, who explained the genesis of the gods as apotheosized mortals. In the last century of the Republic, Epicurean and particularly Stoic interpretations were a preoccupation of the literate elite, most of whom held - or had held - high office and traditional Roman priesthoods; notably, Scaevola and the polymath Varro. For Varro - well versed in Euhemerus' theory - popular religious observance was based on a necessary fiction; what the people believed was not itself the truth, but their observance led them to as much higher truth as their limited capacity could deal with. Whereas in popular belief deities held power over mortal lives, the skeptic might say that mortal devotion had made gods of mortals, and these same gods were only sustained by devotion and cult.
What factors sustained the beliefs in gods according to Varro?
devotion and cult.