It likely has a lot to do with how rigorous the Cuban amateur system is. You are not fighting for yourself and your personal glory, you are fighting for Cuba. When you stare into the eyes of an opponent, you are making the fight about you, making it personal. This makes you less cool and calculated. Makes you less of a fighting machine. If you look at Rigo, Solis, they either stare down or stare through the opponent as if they're not there. It's extremely effective against guys who try to intimidate them, as they realize these are not boxers you can intimidate.
And because when you stare your opponent down you're playing their game. There's no need for that or for opening yourself up to mind games, you've done your work in the gym and you trust your skills. **** the other guy and his staring nonsense. I only look an opponent in the eyes if I've landed hard and want to see if they're hurt/scared so I know to jump on them. Other than that I have no use for their eyes, sparring or otherwise. Any idiot can project false confidence through a staredown.
The media makes him confident. They have him a 100-1 favorite. Donaire can't fight at all, but Rigo is the best fighter of all time, if you don't believe me just ask him.
He's trying hard to convince himself that he's the greatest fighter ever, that his chin isn't made of pure candy glass, and that the 11 dudes he's beaten are P4P elite fighters and not a bunch of nobodies, like they are He's just trying to disguise his fear
Like everyone has said he is the best amateur boxer ever and so far nobody has been able to defeat him in the pros so he has the right to call himself the greatest boxer in history. In terms or pure talent, he is right up there with the best of all time and his defense is top quality.
If he's not confident then why even show up? When you're at an elite level like Rigo of course you're gong to be confident and think you're going to win.