I could now hypothesise about God, extra-terrestrials, or just an amazing series of coincidences that made us who we are. I could, but what would be the point. Let's put aside the supernatural / extra-terrestrial element for a moment and assume accounts of these Gods are related to people. Who were they?
It is not implausible that hominids isolated or segregated from one another may evolve at different rates, and in different ways. We can see this today if we look at indigenous peoples around the world. A good example is how the Chinese 'evolved' at a different rate to the west. It is often just a case of who invents what and when. The four great inventions of China - paper-making, printing, gunpowder and the compass - took them down one route, but they were heavily restricted in some areas particularly in their inability to make glass.
There has always been a mystery about 'sea-peoples', Minoans, Phoenicians, Mycenaeans, etc. In addition there are the Dorians, Ionians, Aeolians etc. It is considered a mystery yet much literature states these people are Aegeans. They are ignoring the fact the Aegean Sea once supported a significant landmass. This is the one missing link in the chain that would give clarity to so many things. Fair enough if it was just one thing the hypothesis gave weight to, then it would be folly to give too much credence. However, it then explains so many other possibilities that are routinely dismissed and is foolish to ignore. On that basis, 'Atlantis' was a large Aegean Island where Atlas (son of Poseidon) was first king.
Poseidon was considered one of Olympian Gods and it was his people (and the other Olympians) who were responsible for so many technological advances throughout the Bronze Age. These Olympians were pretty smart people and with all the problems in the surrounding regions, it would make sense they stayed insular and had a closed door policy towards immigration. The evidence of trade is there, but I would imagine little other contact with peoples they considered barbarians. In a somewhat ironic twist it would soon be the Atlanteans who would be forced to migrate.
It is difficult to imagine the Aegean with lowered sea-levels yet vague references in Homeric tradition speak of unnavigable waters, swamps, and salt lakes. This sort of terrain would serve to isolate an Aegean landmass except from the south where the Sea of Crete afforded access to the Mediterranean. As sea-levels rose and the island began to sink, mass migration occurred in stages over several centuries.
Zeus was a younger brother of Poseidon, but we have to go back even further. When we get to the Titans things get a little fuzzy and the Gods start to lose their human characteristics. Logically it is impossible to go back before the Titans because any information would have to come from the Titans themselves. Some information could have been filtered via the Olympians but if so it would likely be very sketchy. We have to start somewhere but I'm not going to analyse various creation myths, simply because I cannot find one that is plausible without making massive allowances for symbolism and ambiguity.
'Everything came from Chaos', okay so far so good. Chaos was the great void or nothingness, I think even creationists can agree with that. Pretty much everything else followed, darkness, light, sky, earth, etc. These are all natural elements and are readily dismissed as having a consciousness, for want of a better way to put it. The Titans were the offspring of Uranus and Gaia, in effect they were the children of Father Sky and Mother Earth. If prior to these there was some divine connection, it is lost with the Titans. Mythology itself tells us the Titans and all that follow have Earthly origins.
For a civilisation to develop to such an extent, it must have been around thousands of years. Perhaps Plato wasn't so numerically challenged after all. One thing I do agree with is the fact Plato stated there were more than just one deluge. The first would have been when the Atlantic Ocean breached the Mediterranean wall. It would have had devastating effects all around low lying coasts and the Aegean area was particularly susceptible.
Ever wonder why the Olympians were supposedly based on Mount Olympus and the Titans on Mount Othrys? If all the land around me was sinking, I'd seek some nice secure high ground. The Titans and Olympians were most likely among the first evacuees from Atlantis. Nor were they the Titans and Olympians we know. The first evacuees could have left as early as 2500 BC or as late as 1800 BC. I base these dates on significant advances in technology, fermenting, metallurgy, etc. seen on mainland Greece, Crete, Egypt, Mesopotamia, and even as far as India. There are different dates for various migrations. Attica saw Hellene integration around 2000 BC, the Dardanelles 1900 BC, Crete 1900 BC and the Peloponnese in phases over a 200 year period.
In Plato there may be no suggestion of the Gods being the actual inhabitants of Atlantis yet there is much stating their descendants were. For an indeterminable period Atlantis thrived, until according to Plato things turned sour. When you look at all the scant information as a whole, it is easy to see what happened and why. There was a lot more to the story than just the account Plato gave us.
I'm not totally dismissing the idea these 'Gods' were actual Gods, spacemen, whatever. They still could be but the point is, they don't necessarily need to be.