Why does ellison develop in such detail the scene between the invisible man and sybil?

In the movie invisible man it’s basically about a girl who sees this invisible figure which only she can see nobody else until the end of the movie Ellison is like a sound in a speech that your writing in the movie Sybil she basically suffers from a disorder there both crazy in some sense if that makes sense

To describe a new way of thinking that could be relied on