You said it yourself. One would expect that the messages would get garbled over time. Yet, looking at the Vedic and Judaic tradition reveals that their esoteric core is word for word identical. Now, consider:
1) Vedic chant, the oldest unbroken oral tradition in existence that is known to preserve Vedas to a T, goes back to at least 1200 BCE
2) there are no known examples of animism evolving into monotheism or non-duality in Americas, Africa, Europe, and east Asia (Taoism would be interesting case study though)
3) it just so happens that, according to the lore, Abraham brought proto-Judaism from Mesopotamia (Ur), the home of Zoroastrianism
4) Judaism emerged in Levant roughly at the time when Zoroastrianism split and developed from a common prehistoric Indo-Iranian religious system
5) Monotheism was introduced to Egypt (Akhenaten and Atenism) roughly in the time of Moses (again around 13th century BCE)
And so on and so forth.
A common cultural ancestor nicely explains all of these inconsistent events: During the Indo-European migration a branch of Indo-Europeans (Indo-Iranians / Aryans) descended into Levant, mixed with local population (Nephilim?)[1], and influenced Mesopotamian culture to the extent that it gave birth to Zoroastrianism (clearly a local variant of some predecessor). While the main branch[2] continued their migration eastward into Pakistan and India, someone (Abraham) imported the non-dual worldview southward into Canaan. During the first exile of Jewish elites (artisans, scholars, "dukes", etc.) this knowledge then traveled into Egypt and briefly influenced it, while Canaan reverted back to polytheism, only to “flip back again” when that small group of elites returned (Moses). And the rest is history.
—
[1] Claimed to be "children of god" (which inevitably translated to local population as Elohim or Anunnaki); took (intermarried) local women; the word itself literally means “fallen ones”, is usually translated as “giants”, but can also mean “warriors”, “the violent ones”, “the ones falling [upon their enemies]", “sons of the rulers", or "sons of the judges".
[2] They were Indo-Europeans after all, and no migration southward took place AFAIK.
