My cynical guess is this was more of an opportunity to be involved in an Oscar bait project.
If she were truly passionate about the subject matter she could attach her name to the project by executive producing or otherwise helping to finance and promote the film. You don’t need big stars acting in a film to get exposure.
Somehow I don’t think a film with this subject matter is likely to be a big mainstream hit anyway. That never stops people like Tom Hanks, George Clooney, and other big names from backing their passion projects.
