kept secret? There have been hints and legends about a previous superior civilisation that the preisthood of Sais knew about and kept secret, and eventually told to Solon ...
Highly doubtful. It's hard for any human, let alone a group of humans, to have kept even basic secrets. The idea that a more complex civilization existed prior to Egypt that we haven't found archaeological evidence of would be remote at best. And considering that none of the other powers along the Med. Sea seem to have mentioned of such a civilization adds to it.
Why not? Every large culture keeps some secret, so why not the Egyptians. Chances are they kept this civilisation secret so that they could exploit its stories and history. perhaps this original culture formed the basis o Egyptian religious stories.
