Egotisim too often leads one to believe very highly in their own abilities and downgrade the belief in another's abilities.

Thus when you play into the this delusion of egotisital thinking, you're allowed a very large curve of hidden abilities.

Such is the shark in a game of pool. Someone thinks they own the table until a hick steps up, drops a couple bills building up the delusion of the egotistical nutter and then takes THEM for all they hold.