The reason for this became much clearer to me after I read “Who Wrote the Bible?” already mentioned several times. If the priest class was trying to centralize worship and to establish monotheism, one way would be to tell stories about how our ancestors were dumb enough to reject God after looking him in the figurative face, so the rejection of their audience is just as dumb. Lewis does something similar in “The Last Battle” where the evil atheists can’t see Aslan.
Of course the comment by the Israelites which was not recorded might have been “I want to see this written up in a peer-reviewed scientific journal!”
To be fair, it wasn’t Moses who defeated God in that story, it was his wife Tzipporah. What that says about her formidability I’ll leave as an exercise for the reader.
