How do IMdB prepare their 'cast lists'?

Reading the cast list for this one has to wonder how the IMdB people usually get this information. Here, remarkably, as "stars" they just list the first three cast members, none of whom plays a remotely significant role in the film or the story. The first is a voice only, supposedly Miss Austen herself, setting the framework for the story, the second a wholly incidental clergyman who makes no contribution to the story at all, and the third is the mother of the heroine who also has a relatively small role as the heroine leaves home in the first scene and doesn't return until quite close to the end. Apparently no-one involved has read the classic novel or actually watched the film!

There are two "stars": Felicity Jones and JJ Feild with six others of roughly equal significance behind them. None of the six are considered "stars" by IMdB and you won't actually see the names of five of them until you click on 'see full cast list'. In fact the cast list as given is simply in order of appearance in the film.