In Othello, there are many moments of chance that help Iago set up Othello in making him jealous.
In Cyprus, there is only a chance that Cassio will fight and lose his position as lieutenant. Through this chance, Iago used this to further his plan. He suggests that Cassio ask Desdemona for help in being reinstated. This is the chance that Iago needed to make it appear that Desdemona and Cassio are having an affair.
There is only a chance that Desdemona will actually agree to plead to Othello for Cassio's reinstatement. When she does, this is the chance Iago has been waiting for.
Also, there is only a chance that Iago will get his hands on the handkerchief. When Iago gets the handerchief, he plants it on Cassio.
There is only a chance that Iago can get Cassio to talk about Bianca. Of course, Othello has been set up to believe they are discussing Desdemona.
Othello is a play involving many moments of chance. The moments of chance help Iago accomplish his plan to make Othello jealous.
CHANCE THAT THE STORM WILL DESTROY THE TURKS SO THAT OTHELLO WILL NOT HAVE TO WORRY ABOUT THE WAR BUT INSTEAD IAGO CAN USE THIS TO KEEP OTHELLO CLOSE AND PLAY WITH HIS MIND AND ON HIS EMOTIONS.