Great research, thanks for sharing!In order to truly understand how ancient myth was transmitted through the ages, I believe we need to first understand the true origins of myth. I've dedicated many years researching a novel approach to developing such an understanding. Check out my three-part video presentation at geographicalimagesofthegods.org and let me know if it helps answer your questions.
You have a valid question; however, there is a fact that must be considered about the ancient Greek myths. My view: Most of them are not the historically original myths. After a myth was created and became known to others, some other Greeks -- in different places and/or times -- modified them or elaborated them or combined some with other myths: they were not statically maintained or transmitted. A pristine/original myth involved the PERSONIFICATION of some natural or historical event, wherefore all myths are anthropomorphic rather than accounts and explanations of natural events [which we call scientific accounts]. Ouranos was the visible sky as well as the sky-god, with superhuman knowledge, will, etc. All myths are imaginative/invented accounts. They reach the height of Hesiod's Theogony (the Geneology of the gods). // The Hebrew Bible is basically a Geneology of Man, an *Athropogony, which starts with two different myths of the creation of humans, the Elohim [=the Gods, the two supreme Gods, one male and the other female] in Genesis-1 and Yahweh in Genesis-2 -- both euphemistically translated into Greek as "Theos", which eventually made all Christians monotheists and enemies of mythological traditions. [........]This is something I always wondered... how were Greek myths preserved and kept the same through so many years? I wonder if the myths were changed over the years and if they actually have remained the same as they were when they first created in Ancient Times.