The quote that made me wonder this was this one by Herma of Aeschylus, “"Even in our sleep, pain that cannot forget falls drop by drop upon the heart, and in our own despair, against our will, comes wisdom to us by the awful grace of God".
I’ve heard similar usage of a singular “God” from other ancient pre-Christianity figures.
Is this referring to the divine logos? The concept of divinity itself?
Can't say about the other cultures, but for the Greeks, it's a little cultural convention filtered through translation. u/Iphikrates has a post on the Greek phrase "the god". And as always, if anyone else wants to give this a post of their own, please don't let this linkdrop stop you!