The imperial cult might derive from the Mystery religions. It's like how Egyptian resurrection applied at first mainly to the pharaohs and only later to common Egyptians. Some of the Greco-Roman Mystery cults were more secretive or elitist than others. The Roman emperors were sometimes deified after their death to symbolize and to celebrate their greatness. But the core idea of the individual's divine value is found in the individualistic Mysteries, which in turn was based, I think, on the neo-shamanic, Axial Age reformations of the Eastern, Middle Eastern, and Western state religions.