Cassio's trust in Iago is what makes Cassio so easily allowed to be deceived by Iago. His character is confident and kind, and Iago uses this to the best of his abilities, as seen throughout the play. His anger towards Cassio is what gives him the motivation to initiate the plan and eventually remove Cassio from his role as lieutenant. Cassio has no doubts and automatically assumes his responsibilities without questioning anything. His trusting character is what Iago uses because of his wariness and ease of deception. Together, all of these explanations create a perfect combination that Iago can take advantage of and trick Cassio along the way..