There are many possible answers to this question. Here are some of the possible reasons: Filmmaking was very different from novel creation. A movie needed to present a lot of information in a short period of time and maintain a tight rhythm and plot development. Fictions usually paid more attention to the plot and character development. It took more time to describe the background and details. These differences may lead to differences in the way the film and the novel are expressed and the rhythm, resulting in differences between the adaptation and the original. 2. The adaptation of the movie required rethinking the storyline and characters to meet the requirements of the movie production. This might destroy the original structure and plot of the novel, making it difficult for the adaptation to be consistent with the original. The film adaptation also needed to consider how to bring the elements from the novel onto the screen, such as how to transform the world view, setting, and character image of the novel into the scenes and characters in the movie. All of these would need to be readjusted and designed, which could lead to differences between the adapted work and the original work. The movie adaptation also needed to consider how to bring the characters in the novel to the screen and how to express the emotions and theme in the novel. This might affect the plot and character creation in the movie, as well as the theme and emotions in the movie. Adaptations may require cuts, adjustments, or additional plots to better convey the theme and emotions of the film. These adjustments might cause the adaptation to be different from the original. A novel and a movie were two different art forms. Many factors needed to be taken into account in adapting a work, including the storyline, the character image, the setting of the world, the theme, and the emotions. Therefore, the quality of the adapted works was often not necessarily proportional to the quality of the original works, which was one of the reasons why there were differences between movies and novels.