Is Othello the cause of his own demise, or does Iago cause his demise, or is it a combination of the two?
Othello has weaknesses like everybody else, but Iago is a genius of villainy who knows how to analyze people and exploit their weaknesses. Othello was an innocent victim of treachery. Iago understood that Othello felt insecure in his relationship with Desdemona because he was an outsider and of a different race. Iago also understood that Othello was trusting and highly emotional. Iago took advantage of every weakness in every one of his victims--Roderigo, Cassio, Desdemona, and Othello. He knew how to play one against the other. He knew, for instance, that Othello's great love for his beautiful wife could also be a source of great jealousy. He knew that Desdemona's friendly relations with Cassio could be made to look like something sinister. He knew that Cassio's womanizing could be used against him. Actually, Iago is a far more interesting character than Othello or any other character in the play. Most of the guilt is his.