Harold Bloom

argues that

Iago (Jago, Yago ?)

is an artist

of evil.
The same way that some people enjoy writing songs or filming movies, Iago enjoys ruining people's lives.
He does it with a sense of craftsmanship, appreciating the elegance or cleverness of a particular step in his scheme as much as its final result: incredible suffering for the people he has chosen. Ever notice how he stops every time he does something cleverly evil, to muse on it and tell us how awesome he is? Exactly.

We tend to think of evil

people as being brutal and insensitive
or at least disconnected

from the people they hurt.

Iago, however, is able to hurt Othello so much because he understands him so well. He even grows closer to Othello as his plot progresses. Iago manipulates him so expertly that at times it seems he is actually inside Othello's head". source