How does Iago manipulate Othello in Act 3?

The timing of events is very important in Act III. Iago anticipates and manipulates the other characters so skilfully that they seem to be acting simultaneously of their own free will and as Iago's puppets. For example, it takes only the slightest prompting on Iago's part to put Othello into the proper frame of mind to be consumed by jealousy. Iago exploits Cassio's discomfort upon seeing Othello by interpreting it as a sign of guilt: "…

…of witchcraft or magic. Iago's major mistake, ironically, is that he trusted his wife Emilia and found that she was not as trustworthy as he thought. Although not completely victorious at the conclusion of the play, Iago does successfully eliminate the one character representative of heaven, innocence, and honesty. Yet "remains the censure of this hellish villain" (Act V, Scene II). Finally, everything Iago pretended to be led to his ruin: Honesty, innocence, and love.