Religious institutions are masters of this craft and, having dominated the scene for thousands of years, are able to maintain their illusion.
In the western world, since around 1400 CE, the Heresy laws curtailed any religious dissent, while the Blasphemy Act of 1697 shut the lid on any open religious discussion. You were either in or out, and out was not a nice place to be.
Why this draconian silencing of free speech? Because, if the truth ever came out, the identity and nature of the Christian Church would be revealed (think ISIS).
'The Hunting of the Snark' is but one example of how pre-Christian knowledge was kept alive. Another is William Blake's 'Jerusalem' which condemns as Satanic those that, with their 'mental fight' (brainwashing) and 'sleepless swords' (unremitting violence), built 'Jerusalem' (Christianity) in England. Amazingly Blake got away with it for quite a while, though the powers-that-be eventually copped on and changed the wording of the hymn - 'these' to 'those' - dark, satanic mills, thus proving his point (revel in this climactic hymn with related star pictures here: 'Jerusalem' (note that the Ancient of Days has a rat's tail))
Resistance to the imposed religion is everywhere, if you know how to look, for it is hidden in plain sight, often in the most surprising and unlikely of places. Ultimately the Truth lies in the stars, where it can never be erased, but to keep that Truth alive - to keep the star pictures in our minds - the Resistance had to get clever, very, very clever.
The following video highlights a multitude of ways in which the Resistance manifests, including songs, hymns, art, nursery rhymes and royalty: