But I disagree with the point you're making with faith here. Old gods were believed to be true but also "proven". At the time of ancient Greece, there was no discussion about the existence of gods, the fact that the sun goes up and down was by itself a proof, so be it for the lightning, proof of Zeus wrath.
Faith is an essential part of modern religion because people know there can't be any proof of god's existence, but it was not the case when we had limited knowledge of our world ^^
Don't know about that. Ancient gods were proven the same way people say current gods are proven. And there was discussion in ancient greece about the existence of gods. Some were even atheists. But atheism was a capital crime so they were persecuted and had to hide. But among theists too there was discussion about what were the explanations for things like the sun, lightning, etc. The view that it could have natural causes wasn't uncommon. Of course anyone going too far with it could be accused of atheism.
https://en.wikipedia.org/wiki/History_of_atheism"The first fully materialistic philosophy was produced by the atomists Leucippus and Democritus (fifth century BCE), who attempted to explain the formation and development of the world in terms of the chance movements of atoms moving in infinite space."
"Euripides (480406 BCE), in his play Bellerophon, had the eponymous main character say:
Doth some one say that there be gods above?
There are not; no, there are not. Let no fool,
Led by the old false fable, thus deceive you.[13]"
"Aristophanes (ca. 448380 BCE), known for his satirical style, wrote in his play The Knights: "Shrines! Shrines! Surely you don't believe in the gods. What's your argument? Where's your proof?"[14]"