Oh your example of Violet Evergarden is unfair by the way
- It was probably planned from the start to have a movie
- They already have key visuals / key art / character designs in place
- The animation team probably were already working on the movie before the last episode aired
PS - I'm looking forward to the Violet Evergarden movie - I own the show on JP blu-ray - just hoping it makes it out to the inaka where I am but won't hold my breath. If it's anything like Haikara san ga tooru in won't and will have to wait for the blu-ray