What is it about Fortunato that makes him fall prey to Montresor in "The Cask of Amontillado"?

To me, there is one thing about Fortunato that we can see
clearly and one that we have to guess at.  Both of these seem to have some role in
making him fall prey to Montresor.

The clearly evident one
is his pride.  Montresor keeps giving him the chance to just go home but his pride won't
let him.  Montresor keeps saying that he'll go get Luchesi to see whether the wine is
really amontillado.  But Fortunato is too proud to let this
happen.

The thing that we have to guess at is why Fortunato
doesn't know Montresor hates him.  One guess is that Fortunato is too arrogant and stuck
on himself to even think about how others see him.  Maybe he never even thinks about how
his actions affect others like Montresor.