When in Greek history did the religion go from polytheism to monotheism?
Classical greek paganism existed throughout much of classical Greece’s history. It was only during the Roman era that they saw the spread of monotheism, first in the state mandated devotion to Sol Invictus, then to Christianity. It was not a singular process, but a long, drawn out affair that took centuries. Much of the Roman Pantheon was based off of the Greek ones. Like modern Europe, Greece was considered the primogenitor of civilization, thus were a highly insular society, holding the rest of the world, including their Roman masters, as unwashed brutes and barbarians. Now the Romans were highly tolerant of the religions of others, so much as A: they did not disrupt the public order and B: they offered praises to the Roman gods when mandated by the senate. Because the Greek gods were seen as mirrors to the Roman ones there was little religious strife between the Roman and Greek pagan religions. This is also why there was much friction between Judaism and the fledgling cult of Jesus
