Fortunato's crime against Montresor is not explicitly stated in Edgar Allan Poe's "The Cask of Amontillado." However, it is suggested that Fortunato may have insulted or wronged Montresor in some way, prompting Montresor's desire for revenge.
It is ironic because Montresor is actually planning to kill Fortunato. By toasting to Fortunato’s long life, Montresor is being hypocritical or insincere since he intends to end Fortunato’s life.
Montresor's response to Fortunato's screams adds to the mood of the story by showing that Montresor feels some guilt and compassion for what he is doing. This mood quickly passes and he goes back to being filled with hatred.
This shared interest in wine foreshadows that Montresor might use this to lure Fortunato to come with him to get the Amontillado, so his plan to kill him can succeed.
Montresor drinks to show casualness and to keep up appearances while leading Fortunato into his trap. It helps him maintain his façade of friendship and trust until he can exact his revenge. Drinking also allows him to maintain a sense of control and cunning over Fortunato.
The nature of Fortunato's insult is not explained in detail in Edgar Allan Poe's "The Cask of Amontillado" because the story is a first-person narrative told by Montresor, and he chooses not to disclose the specific insult. This lack of detail adds to the story's ambiguity and creates a sense of mystery and intrigue.
He was thinking about Fortunato's death. Mostly because he wants revenge and wants to kill him
Fortunato seems not to trust Montresor and asks whether he is one of the masons.
The main conflict is that fortunato had done something to montresor and now montresor wants to get back at him by killing him.
In "The Cask of Amontillado," Montresor and Fortunato briefly discuss the concept of brotherhood as they make their way through the catacombs. Fortunato claims to be a member of the Masons, but Montresor points out that he is not, suggesting that they do not share true brotherhood. This conversation serves to underscore the false camaraderie between the two characters as Montresor leads Fortunato to his demise.
Montresor wants Fortunato to drink the Medoc wine to keep him warm and toasting to the success of their endeavor. It helps to loosen Fortunato's inhibitions and lead him deeper into Montresor's trap.
In "The Cask of Amontillado," the main character Montresor seeks revenge against Fortunato for an insult. Montresor manipulates Fortunato's pride and ultimately leads him to his death in the catacombs. The conflict between the two characters is driven by Montresor's deception and betrayal of Fortunato's trust.