As I am sure you know Zeni the Elder produced a definitive paper over a thousand years ago
on some questions that had been troubling sages for eons. These were: do the same gods exist
across multiple worlds in the Material Plane and do these worlds all connect to the
same Celestial (and Infernal) Planes? He did this by journeying extensively in the Planes
and that is why his conclusions are now accepted by most schools of sages. I mention this
because although Zeni produced convincing arguments to explain why there were different ways
the same Gods
were worshipped on different worlds he might be stretched to explain
the religious anomalies that exist on Oerth.
One obvious one is that Pelor is supposed to be dead, slain over a thousand years
ago by a demon! There are other anomalies, however, which I have been able to research,
having obtained access to secret records in the Temple of Athena (how this came about is an
interesting story that I wont go into here). The Gods of Olympus were apparently
the official state pantheon at the time of the Dragon Empire (easy to see why the Temple
is keeping these records secret). At that time the records say Hera slept with her husband's brother Hades
then slew him and even now reigns over Hell as Juno the Damned. Shortly after that setback for Zeus
civil war erupted in the Empire in which the Gods took part. Zeus and Apollo were slain by
demons and had to be rescued from Tarturus by Heracles.
It is not difficult to see why Olympian worshippers on Oerth now consider Athena, rather than
her father, to be
the leader of the Olympian Gods.
I can think of a number of explanations for these stories, one of which is that there
is some time displacement involved in travelling through the Oerth portal and what we are
seeing is our far future in which these celestial events have already happened. The second
explanation is heretical (for a sage) in that it is possible Zeni was wrong (or at least
the multiverse is more complicated than he assumed). Come to think of it there is a third
explanation which concerns 'alternative realities' but perhaps it is actually far too
early to say where the truth lies. As with my other studies I think we are just taking
the first steps of quite a journey but we will no doubt have a clearer picture once your own
planar investigations
bear fruit.