We would expect, for example, that many GODs will participate in the story and not a single GOD, that this GOD will be represented in a statue and a picture and more. If we believe in special divine providence over the People of Israel – evident throughout its unique history – then the question of the historical accuracy of the stories of the Torah and how they develop becomes irrelevant.
The essence of those stories is the divine message that Providence wants us to learn from, not the question of what exactly happened in practice thousands of years ago.
If a “rolling myth” could take natural events and inflate them into such a supernatural tradition, we would expect to find similar stories in other peoples. We do not know of any similar tradition of a people that tells how its GOD was revealed to the people, led them continuously over many years and so on. If such a story can be created with such simplicity, why do we not know many more such stories?
The uniqueness and anomaly of the Jewish tradition indicates that this is not a natural story that has swelled over time, but is indeed unusual and special based on historical realities as viewed by the people of the time of the occurrences.