It would be entirely wrong to think of atheism as a new phenomenon.
Maimonides (12thcentury) says, ‘[T]here are three different opinion on Prophesy. I will not notice the view of the Atheist; he does not believe in the existence of God, much less in Prophesy..’ M Friedlander, The Guide of the Perplexed of Maimonides,ch xxxii, p161. Hebrew Publishing co., New York.
Plato (4th century bce), writes about a believer chastising an atheist: “You and your friends are not the first to have held this view about the gods! There are always those who suffer from this illness, in greater or lesser numbers.”
https://www.theguardian.com/books/2016/feb/17/atheism-has-ancient-roots-claims-new-study