Why do Cinematic Universes that aren’t Marvel so often Fail?

We don't know that Kane was alone when he died. The short scene goes by in a dream like fashion in, mostly, extreme close-up. We have the shot of Kane's mouth saying "Rosebud," another close shot of the globe falling from his had and smashing on the floor in slow-motion, then a cut to a shot of a nurse coming through the door. We never see the entire room, the mode is expressionistic, and there is really no reason to think Kane is alone. This is a meme that cropped up a long time after the film was released.