Lines 420-436: Why is Polyphemus surprised by the fulfillment of the prophecy? What does the Cyclops's characterization of Odysseus as "small, pitiful, and twiggy" suggest about the value of "brawn versus brain" in a conflict?

The prophecy said that Polyphemus would be defeated by a man named Odysseus, so obviously he was expecting someone huge and strong to fight with him, but when Odysseus defeated the cyclops using his brains only, he was really surprised because he underestimated his power