Recently, on my UTube feed I got a video on ancient Rome and religion. The gist of which was that religion was inseparatable from the state and society. For example, the treasury in ancient Rome was also the Temple of Saturn. Atheism was almost unthinkable when society and religion were so tightly intertwined.
Of course, ancient Rome isn't ancient Greece, but I thought they might be similar and sure enough they were. Ancient Greek religion was deeply intertwined with Greek society in a similar way as in ancient Rome. It was the glue that held separate city states together with a common Greek identity. As this video shows:
Epicurus was and has widely been criticized for atheism, but he very likely was a theist with a different and realistic as opposed to idealistic view of the gods than was common. He even says so: