Because the acts or events of true history have not that magnitude which satisfieth the mind of man, poesy feigneth acts and events greater and more heroical.
It's a great historical joke that when the Spanish met the Aztecs, it was a blind date made in serve-you-right heaven. At the time, they were the two most unpleasant cultures in the entire world, and richly deserved each other. Still, the story of how stout Cortes blustered, bullied and bludgeoned his way to collapsing an entire empire with a handful of contagious hoodlums is astonishing.
The history of mankind interests us only as it exhibits a steady gain of truth and right, in the incessant conflict which it records between the material and the moral nature.