Where is there situational irony 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
 

What is the question here

Shark is the answer