It seems that the evil cunning Iago is not as super-intelligent as he thinks he is in the play 'Othello' by William Shakespeare. Yes, he is sharply observant, seeing as clear as day the faults, frailties and weaknesseses of others. He quickly works out Othello's vulnerable Achilles Heel - his insecurity. He can think ahead, he can manipulate and flatter and exercise control over other people because he sees what drives their behavior. For example, in Roderigo's case it is infatuative puppy-love for a married woman - Desdemona. But he is not infallible. For example, he grossly underestimates Roderigo' character. Roderigo is temporarily blinded by the Cupid's arrow of love, but then we see in hindsight that the scales were beginning to fall from his eyes. He was no permanent fool, just a temporary one.
I certainly think that near the beginning of the play, most of the audience would see Roderigo as a fool and love-struck fop. He believes that Iago--who clearly explains in Act 1, Scene 1 that his actions are purely self-serving--will help him win Desdemona's love (now a married woman). He does whatever Iago tells him to do: spends money, disguises himself, and travels to Cyprus (a much more dangerous location than Venice).
However, when all the key characters arrive in Cyprus, Roderigo begins to see the truth about Iago. Nothing that Iago has promised him is coming true--he has lost all of his money through traveling and buying jewels (which Iago has kept for himself instead of giving to Desdemona). Still, Roderigo does agree to do complete one last action for Iago. He will kill Cassio. But, after the events of Act 5 occur, and Roderigo is killed by Iago, a note written by Roderigo is discovered which exposes Iago's dastardly scheme. It seems that Roderigo did not completely trust Iago after all and carried out his threat to expose the villain for who he really is.
So, when one considers that Roderigo--the one whom Iago played for a fool--discovers Iago's true character and that Othello (a military general), Desdemona, Emilia (Iago's own wife), Cassio, and numerous Venetian officials do not recognize Iago's true intentions, then he is not such a fool, is he?