I didn't either until an English teacher in college who was covering Shakespeare's Othello made the point. She interpreted Iago as the poster-child for unfettered praise heaped onto a person through their life. When they reach their peak as adults they are confronted with the tragedy of being mere second-best at something and that is the toxic frame of mind that can fester into the jealous rage that exemplified Iago's character. He conspired to destroy a national hero just because he cast a long shadow.

Enough people tell you you're the greatest, and you believe it, you may even be tempted to kill to make it so.