Small animals suitable for experimental use must reproduce fast and their genes should be as similar to humans as possible. Some small animals reproduce fast but have few genes similar to humans. 
some fast-breeding small animals are not suitable for experiments.
To get a good box office, a movie must be both watchable and successful in the market release. Some movies with good box office are actually not very watchable. Therefore, the reason why some movies are good at the box office mainly depends on success in the market release.