The old adage is that truth is stranger than fiction. And it’s true.
Just because something happened, that doesn’t make it a good story. And it doesn’t give reason for putting it in a story. The reason truth is stranger than fiction is because fiction has to be believable.
Fiction operates on telling a story around one thread or idea. The best biopics are not the ones that stay close to the actual events, but ones that pick the relevant parts of a biography to tell a story, staying true to the story arc and the characters.
The Johnny Cash and Ray Charles biopics were hailed as a success because they both stayed true to the story that they’d picked from the musician’s life. The James Brown biopic had amazing performances but lacked the narrative thread to tie it together, ultimately failing to tell an interesting or moving story.
The fact that something really happened doesn’t make it exempt from rules of narrative. It just gives you material to work with.