According to Christianity, Lucifer fell from Heaven because of the sin of pride. Like Nimrod in Canto XXXI, Lucifer challenged God’s supremacy. Unlike Nimrod, he had everything. He lived in Heaven and was the most beautiful of God’s angels. And God’s favorite. But that wasn’t enough. Get the picture? We’re talking arrogance beyond belief.
His punishment fits his crime. For his pride in moving against God, he’s now permanently frozen. Appropriately, his pride only worsens his imprisonment. If he would stop flapping and chewing for a second and actually use his brain, he might figure out that maybe if he stopped waving about, all that ice would melt and he could wriggle his way out. However, stopping his flapping would mean no longer struggling against God; it would be an admission of defeat. He can’t stomach that.
So Lucifer turns out to be just a figurehead, not really an individual with a unique character. The biggest, baddest sinner of them all turns out to be not so bad. (He’s big; we’ll give him that much.) Or at least, Dante doesn’t spend a whole lot of time characterizing him in the way he does Vanni Fucci or Guido da Montefeltro. As readers, we don’t hate Lucifer in the way we despise the pettier sinners.
If you know Dante, you know this isn’t accidental. The point, then, is that this is what evil is, nothing more. Evil’s most powerful agent is stuck in a lake of ice, flapping his wings desperately to try to get out, and his flapping only entraps him more. Hmm, Lucifer doesn’t sound all that powerful to us. But there’s the point: when compared to the goodness of God, who can express His will in nature, in mankind, and in basically everything, the evilest guy of them all can’t even move. Evil can’t hold a candle to good. The nature of evil is not action that counters good, but a void. A simple lack of virtue. It has no agency, no way to act. That’s how helpless evil is against good.
Virgil expresses his contempt for evil and its powerlessness when he refuses to spend more than a few minutes gazing at Lucifer. Virgil says virtually nothing about Lucifer, does not ask him to speak, and then tells Dante it’s time to leave. Virgil’s behavior suggests that the ultimate evil isn’t even worth dwelling on.