Excellent question. What is driving Iago, anyway? He is full of explanations and motivations, and yet few of them make much sense and we’re left wondering if he has any real motivation at all. He very early on tells us straight out: “I hate the Moor”, but his reasons keep shifting and changing. He makes horribly racist jokes – could he simply be a violent racist who hates Othello for his race alone? But then he tells us he is afraid Othello is sleeping with his wife – well, that would certainly be a motivator but it isn’t true and his fear seems irrational; how could Othello be carrying on with Emilia, even if he wanted to? Where? When? Iago also tells Roderigo of his resentment at being passed over for the lieutenancy – this is the first thing that seems reasonable to object to; after all, Iago worked hard for that position, other authorities advocated for him to get it, and he seems only to have been passed over because Cassio was from a nobler class. At other times, though, Iago’s hatred seems to transcend any bitterness about a promotion, so…where does it come from? Iago is scary precisely because he seems to have a great many grievances and yet none at all, a dangerous man who fixates on destroying someone and grabs at any excuse to justify it.