Much as I dislike the fact, "Hollywood," meaning the big motion picture studios, is like any other business: the studios exist to make money. The studio heads only greenlight projects they believe will make money for them, based on their perception of the tenor of the times, what the public wants to see, who the public wants to see, what the public wants to see the whos in, and the drawing power of the stars and the director, at that time. They aren't always right.
Example: Orson Wells' The Magnificent Ambersons. Students of film rightly regard it as one of the most important films Hollywood ever made. But it bombed at the box office when it was released, because the tenor of the times had changed from when Wells began filming it, and people didn't want to hear a film with a peaceful message right after Pearl Harbor. It bombed at the box office.
Example: The Philadelphia Story. When we think of Katharine Hepburn today, the first words that come to mind are "magnificent actress." But in 1940, when Hollywood thought of her, the words that came to mind were, "box office poison." Hepburn saw the play in New York and bought the film rights, hoping to use it as a vehicle to jump-start her career. When MGM went to buy the play, they found Hepburn already owned it, and if they wanted to film it they'd have to cast her, with her having some say in what was done with the material. She insisted on a top-flight director who could handle comedy, and got him. She insisted on a sold cast, and got it. And she insisted on playing Tracy Lord, the female lead, or no deal. The film version of The Philadelphia Story is a marvelous comedy without being slapstick. The public loved it. It was nominated for six Oscars, including Best Picture and Best Director; and won two - Jimmy Stewart for Best Actor, and Donald Ogden Stewart for Best Screenplay. Hepburn got a Best Actress nomination out of it herself, and her career never went off-track again.
Example: 2001: A Space Odyssey. Hollywood thought that the American film public was ready for a cerebral science fiction movie that did not depend on ray guns and bug-eyed monsters from another world. Hollywood was wrong. Though it won one Oscar for Best Special Effects, it did not win any of the big Oscars like Best Director or Best Original Screenplay (though it was nominated for both). As far as making money, don't make me laugh! It took something like 15 years for it to make back what it had cost to produce 2001. The lesson, "Don't make big-budget sci-fi movies, they don't do well in theaters" was so well learned by Hollywood that when a guy came along 8 years later with a sci-fi script, he had an awful time getting the financing to make his movie. The studio was so sure it would bomb at the box office, they didn't even ask for rights to produce action figures, novelizations, soundtrack albums and things like that, and let him keep them. I'm sure you've heard of that movie: a little epic called Star Wars.
As you can see, Hollywood can't always pick 'em. But that doesn't mean they would go for a biopic of Charlton Heston, either. If he'd been involved with the Brady Campaign, there wouldn't be a problem here. But because he went from liberal to conservative and not the other way around like Ebenezer Scrooge, there's no way they'd fund it. The last Hollywood biopic I can recall that made money was Gandhi, and that is a four hour long crashing bore of a movie.
Which just goes to show I can't pick 'em, either.