Back in 2009, after facing criticism over the historical inaccuracy of Braveheart, Mel Gibson said on the story of William Wallace:

"We romanticize... We shifted the balance because someone’s got to be the good guy against the bad guy; that’s the way stories are told."

Even if two bad guys are fighting against each other (Wallace was not a good guy in history but was fighting against the English, also the bad guy), one has to be the victor, and in telling that story, we romanticize it to attract viewers. So you hire an attractive actor, soften the character's badness, and focus on the story. Voila! The popularity of Braveheart. And every other film that's done this.