What is the purpose of the author's description of Fortunato's clothing in "The Cask of Amontillado"?

Poe dresses Fortunato as a fool because he followed Montressor into the catacombs in hopes of sampling a rare bottle of wine which are the actions of a fool. In the end he allows Montressor to manipulate him and kill him without realizing the real intentions of his "friend" until it is done