He's not, he was tricking him into thinking he cared
Montressor needs to make sure that his plan goes off without a hitch. If Montressor were to act indifferent to Fortunato's health, Fortunato may suspect that Montressor was up to no good.
Montresor wants to gain Fortunato's trust so that he can lure him into the catacombs and exact his revenge for the perceived insult he believes Fortunato has committed against him. By pretending to be a concerned friend, Montresor is able to manipulate Fortunato into following him to his demise.
The mood in the scene is deceptive and foreboding. Montresor appears friendly and concerned for Fortunato's well-being, but there is an undercurrent of malice and manipulation as he lures Fortunato into his trap. The tension builds as Montresor leads Fortunato deeper into the catacombs, foreshadowing the dark fate that awaits him.
Montresor blames the sickness in his heart on the dampness of the catacombs, which is interesting because he just entombed Fortunato behind a brick wall leaving him to die. The murder of Fortunato does not bother him, but dampness does.
Montresor manipulates Fortunato by appealing to his ego and vanity, leading him to believe he is an expert in wine who must taste the Amontillado. Montresor also plays on Fortunato's pride by pretending to be concerned for his health, which further convinces Fortunato to follow him into the catacombs. Overall, Montresor uses psychological tactics to exploit Fortunato's weaknesses and ultimately lead him to his demise.
Frank Fortunato's birth name is Fortunato Francesco Musorrafiti.
Fortunato Frattasio is 6'.
Fortunato Chelleri died in 1757.
Fortunato Felice was born in 1723.
Fortunato Felice died in 1789.
Fortunato Arriola died in 1872.
Fortunato Arriola was born in 1827.
Fortunato Anselmo died in 1965.