the whole pantheon is and was known by a large part of population, if not by everyone, and for centuries.

That could also very well be a case of later populations coming to normalize and accept what was originally only a smaller belief-set.

For example, the early Christian interpretations no doubt varied a lot, such as with the Essene sect, and others. And yet if you look at how people commonly view Christianity today, it's hugely dominated by the tradition of the Roman Catholic Church, going back ~1700yrs, and by Protestantism, going back ~500yrs. Most such people still don't have a clue about all the other ancient texts and oral traditions which were decided not to be included in the major bible line, such as the other gospels.

See the other comment here for more, in which a book focuses on this...