How about scene by scene commentary for cats on a youtube video. Sports have this and you can watch old sports matches on youtube. Right now youtube would block it and my use case extends the fair use by quite a mark. You have to understand that under DRM even seeing the movie with family and friends is illegal.
What exactly about being in the public domain would help a movie "gain more" if it hadn't had a successful box office run previously? "GPL-based businesses making billions" does not strike me as a meaningful comparison here. ("Well, 'Cats' is a fiasco, but if we give it away for free we can make a killing selling enterprise service contracts for it!")