While some fantasy movies strike gold at the box office, a lot of stunning entries into the genre end up flopping despite their immersive worlds and effective mythology. Fantasy is a tough genre for filmmakers to succeed in. While horror movies can be made relatively cheap, fantasy tends to require a lot of elaborate world-building. For authors, this might mean a few lines describing a lush kingdom or a desolate wasteland but, for directors, it can mean a lot of money. Fantasy movies are often a big-budget endeavor, which makes them a high-risk investment.
https://screenrant.com/fantasy-movies-box-office-bomb-fail-great/