Why is it necessary for the author to introduce a new character Michaelis in Great Gatsby?

Michaelis serves to provide an outsider's perspective on the tragic events that unfold in the novel, particularly the death of Myrtle Wilson. Through his reactions and interactions with other characters, Michaelis offers a contrast to the main characters and adds depth to the exploration of class and morality in the story. Additionally, his presence helps to highlight the theme of social isolation and disconnectedness that permeates the novel.