Regarding Shakespeare's Othello, in light of Iago's original plans, in what ways do those plans fail?

In Shakespeare's Othello, Iago hates
Othello and hopes to see him destroyed.

Iago believes that
if he wants to get to Othello, the best way is to go through Cassio, who was promoted by
Othello, over Iago. So Iago stirs things up so Cassio will find disfavor in Othello's
eyes, hoping he can take both men "out." When Cassio laments what has happened, Iago
assures Cassio that Desdemona can be of assistance in repairing his damaged reputation.
In getting Desdemona to speak on Cassio's behalf, Iago is able to plant seeds of doubt,
while leading Othello to suspect an affair between his wife and
Cassio.

All the while, Iago plays one character off against
another in order to find a way to pay back Othello. Iago hopes to have Roderigo (who
once loved Desdemona) kill Cassio; Roderigo attempts this thinking he will then have a
better chance getting Desdemona in the end. Roderigo attacks Cassio, who does not die,
but then, under the pretense of rage at what Roderigo tried to do
to Cassio, Iago kills Roderigo.

In terms of Iago's failure,
Cassio does not die. However, Iago drives Othello into such a jealous frenzy, believing
Desdemona unfaithful to him, that Othello kills his
wife.

As news begins to come out regarding Iago's
machinations, it becomes obvious that Desdemona was innocent; this is confirmed by
Iago's wife, Emilia. Othello tries to kill Iago, but others there prevent him from doing
so. Iago then kills his wife and attempts to run away (though he is
caught). Othello is told he must stand trial for taking Desdemona's
life, but being devastated by what he has done, he takes his own
life.

At the end, orders are sent by Lodovico, for the
execution of Iago. Iago is successful in destroying Othello, but Cassio is
not killed as Iago had hoped, and in the end, Iago is himself put
to death.