Keep in mind the IE gods all have a common PIE root. It It was later that they diverged, re-converged, borrowed characteristics. Not unlike the IE languages themselves.
Have you ever read anything by Robert Graves? In his books
The Greek Myths and the
White Goddess he spends some time tracing how the deities relate to each other through the migration of populations over Europe, the Near East, and India. There are scholarly critiques of Graves' writing, many of the criticisms he would probably accept as he always viewed the subject through the lens of a poet. His main thesis in the
White Goddess is that the original religion of Europe was a massive cult of the Great Goddess, worshipped in tripartite form as maiden, mother, and crone. Now, even if you have never read Graves, that probably sounds familiar to you. Wiccans have taken this idea (Graves is not the only source for the claim) and ran with it. Personally, I have my doubts. Goddess worship was obviously important in ancient Europe, many important and powerful female deities were worshipped across the continent. However, looking at Mycenaean art we can see evidence of a religion that was already more diverse than simple "goddess worship." The names of many gods, including Dionysos, appear in Linear B script. The latter is particularly important because some argue that Dionysos was a later deity imported to the Greek world, possibly of Asiatic origin. However, seeing that the Mycenaeans already knew of and worshipped him, we know he is an ancient god and would be hard-pressed to claim him as being foreign.
https://en.wikipedia.org/wiki/Mycenaean_religion
Sorry, I digress.