Othello sabotages himself, repeatedly. His lack of comfort in the domestic sphere leads him to make several critical errors, not the least of which is his lack of faith in himself. He trusts Iago all the more because he has no faith in himself or his judgement where women, marriage, or city life are concerned.
When it all comes down to it, Iago only spins the web of lies. Othello has to choose to believe it, to doubt himself and his wife and Michael Cassio. It is, after all, Othello's hand which kills Desdemona, not Iago's.
Tis is said becuse Othello is the one who killed himself and his one and only wife because he believed Iago. Iago finally got what he wanted.. He was actually Othello's enemy but Othello had no idea about that.