In the novel, Nineteen Eighty Four, the point is made that ‘who controls the present, controls the past.’
This means that history is flexible. Those who are hold power can cut and paste past events to create a certain image. When there is change in the power structure history is reprocessed to match the current ‘narrative’.
As most people accept what they are told, few doing anything near to research, History is the easiest realm to manipulate. Few people question events that they are told happened decades, centuries ago. Few test if what is being promulgated now is actually true.
Most people will not apportion the time or interest to investigate if an event really happened, or happened as stated. As years pile up as boulders truth becomes more obscure. The culture of the present casts a blanket over the past. People automatically believe what they are told or read which matches what they think is real.
“Certain” this is what happened or how or for what reason, they will not deal with contradictions, ignore provable facts, and persist in the ‘history’ they have been spoon fed.