Let's take a look at the unquestionable failure that was Herbie: Fully Loaded from 2005. I know that we all know it's terrible, but I swear I'm not just picking on an easy target; remember, no one WANTS to make a bad movie, so let's find out how it happened. Our younger readers know Lindsay Lohan as a sort-of porn star and constant reminder of our society's sick and destructive relationship with pretty things, but before that, she was an actress who was paid lots of money to be in normal movies. In 2005, she was at the peak of her popularity and had signed on to a reboot of the Herbie franchise (a wildly popular property wherein a car has a soul and can communicate with humans and we promptly decide to make it perform free manual labor for us, because our society also has a sick relationship with magic cars), written by the impossibly hilarious duo of Thomas Lennon and Robert Ben Garant (The State, Reno: 911, Night at the Museum). Popular actress + popular pre-existing franchise + hilarious writers is, by all sense of logic, a formula that should yield a perfect summer blockbuster.
Have you seen that movie? It is just unwatchable.
That's because Lennon and Garant, the writers who were hired to write the movie, got fired after they'd turned in their first draft. According to their fantastic book, Writing Movies for Fun and Profit, they had pitched their take on the script to one studio head, who loved and subsequently bought it. When it was time to hand in their script, they were told to give it to a different studio head, one who didn't get the script, so he told them to make a number of changes, which they did. Then the original studio head came back and (rightfully) said, "Hey, this isn't the movie we discussed; you're fired." Then NEW writers were hired to "fix" it (these writers likely won't be mentioned in the credits, by the way). Then those NEW writers were fired by a DIFFERENT studio head, and ADDITIONAL writers were brought on, with a focus on pleasing some OTHER studio head and not getting fired.
Here's a visual representation of the whole process.