Othello - Reflective Entry

The end to Act V did not surprise me all that much since this play was carried out as a typical Shakespearian tragedy. What was unexpected was Iago's silence in the last part of the act. I was expecting more rebuttal from Iago, but instead he merely says, "Demand me nothing. What you know, you know. From this time forth I never will speak a word," (V.ii.302-303). At any other point in this story, Iago would have fabricated an explanation to get himself out of this situation. In this last scene though he decides to just remain silent. I do not understand what caused this change. I cannot see Iago feeling guilty for anything he caused, especially since he stabbed his own wife just minutes before, so I do not know why he would decide to let himself be taken in so easily.