Heliopolis).
Greco-Roman influence is by far the greatest on the Cosmology, but it's also the greatest influence on Western Civilization, so it makes sense in a it'd have the greatest influence on D&D, Archons come from Greek Heremetism/Neoplatonism inspiration (Gnostics influence would have them much darker), Aborea is Olympus + Elves, Gehanna is actually a Greek word I think but for something in Judaism, Tartarus/Elysium/Hades are obvious, River Oceanus is Greek as well. The Norse have Ysgard, but also the second layer of Hades oddly.
As for Heliopolis being a Greek name for an Egyptian city, most of the Egyptian/Mulhorandi Gods use their Greek names, Bastet being an exception. Example they use Isis instead of Aset as the name for a Goddess.
But this is fine, even alot of Pagans use the Greek names.
As for why no Duat, I'm not sure, but the I don't know enough about the process through which the D&D Cosmology came to be.