Throughout the entire play, Iago does everything possible to gain the trust and respect of Othello.
Iago begins to tell Othello everything that has happened between Cassio and Desdemona.
Again Othello seems a bit skeptic about believing Iago but of course, everything Iago says is happening, happens and becomes somewhat true.
Othello is believing everything Iago tells him and I don't blame him because if one of my best friends tried telling me something was going on and he had good