In chapter 23 How does Mary Shelley portray Victor Frankenstein after the death of his father, who died a few days after learning of Elizabeth’s death? Why does Shelley portray Victor in this way?

Victor has no memory of the time that immediately followed the death of his father; he later learned that he was kept in a miserable asylum, having been declared mad. I think that Shelley wanted to illustrate the depths of Victor's anguish. He could no longer process his tragedy.