Look at Shakespeare's "historical plays". Some were meddled with for propaganda reasons, or to flatter certain influential families by making their ancestors look good, and some just to make the story more interesting.

This was one of my grandfather's pet peeves. He was a very well educated man who been born in the 19th century, and he felt that it was scandalous that American kids got all their history from the movies, which somehow managed to insert a love story into every historical drama. He could understand the concept of a fictional account set in historical times, but he assumed any departure from the history itself would be instantly obvious to the audience. Fat chance.

He also was astonished at how classic literature was often "adapted" for the screen, so that the plots of famous novels were barely recognizeable. Of course, Shakespeare did a lot of that too, as did the opera he loved. Perhaps the Spanish literature and drama he was more familiar with had a stronger tradition of remaining faithful to the original material.

He still held to that quaint notion that the purpose of popular media was primarily to educate, not entertain. And he found it baffling that it could not seem to manage to do both profitably.