Othello is the victim of his own demise. He believed Iago over his own wife. Othello fell victim to Iago's twisted, evil plan. Othello wanted to believe his wife, but Cassio had the handkerchief. This was the "ocular proof" that Othello needed to believe that his wife had been unfaithful.
Othello did not trust his loyal wife. He did not have faith in her. He had low self esteem. He expected her to betray him because of his own weaknesses. Othello was not secure in his marriage. It was easy for Iago to deceive him. Iago was also a mastermind behind the plan to deceive Othello.
It was as if Othello was waiting for his wife to be unfaithful. He did not have confidence in himself to keep his wife happy:
But Othello's confidence starts to slip when Iago begins to work on his psyche, intimating that Desdemona and Cassio are having an affair.
Othello gives in to Iago's lies. Othello begins to believe the worse:
But Iago's "medicine" (IV.i.46) soon begins to work, and Othello begins to question how Desdemona could continue to love him. After Iago has suggested that Desdemona has already deceived her father and Othello, the Moor begins to think Desdemona's betrayal of him is inevitable given his skin color, greater age, and lack of courtly charm (III.iii.263-268).
Othello is victim to his own demise as he loses confidence in himself. Othello begins to think that Desdemona's betrayal of him is inevitable. After all, he is of greater age and he is black and he lacks courtly charm. Othello gives in to negative thoughts and falls victim to his own demise:
He begins to act as if her unfaithfulness is a certainty, bemoaning that "Othello's occupation is gone" (III.iii.357).
Othello falls victim to his own demise. He believes Iago over his loyal wife. He believes lies above his own wife's reasoning. Othello is a weak man when he cannot trust his own wife over Iago.
Yes,othello is the victim of his own demise. He trusted the wrong person Iago, he should have trusted his loyal wife.