In the novel, Nineteen Eighty Four, the point is made that ‘he who controls the present, controls the past.’
What this means is that history is flexible. Those who are in power can cut and paste events, or leave them out, to create a certain image.
As people accept what is called history as fact, there is little peering behind the words to check or test if what was written is actually true.
As few people have the time or interest to investigate if this even really happened or happened as stated, years pile up as boulders.
The culture of the present casts a blanket over the past so that people automatically believe what they are told or read which matches what they think is real.
As people are certain this is what happened, how it happened, they will not deal with contradictions, ignore provable facts, and believe the ‘history’ they have been spoon fed.