Seeing and Refusing to Believe
Capernaum was the base for Jesus and His disciples when they were in the Galilee area. The miracles He performed were the talk of the town; and they clamoured to see more. But did the miracles make the town's people any more holy? No! Jesus said that their refusal to believe in Him would be the crushing evidence against them when they came to Divine judgement.
Sodom was a very wicked pagan city and yet God was prepared to spare the town if only ten people believed in Him (Genesis 18:16-33). Yet despite 'righteous Lot's' presence in Sodom (2 Peter 2:7-10), the city was destroyed. However, Jesus said that if they had seen His miracles they would have believed. Such was the awesome power displayed by Jesus. But the people of Capernaum only wanted to be amused by the miracles, and not follow the signs to put their trust in Jesus.
It is not popular to talk about judgement, but Jesus did. He was clear that our response to His Word and the evidence of His power will provide the basis for God's judgement on the Final Day. Even some pagan and notoriously wicked people may be treated less harshly than some well informed and apparently God-worshipping people who refuse to trust Him (Isaiah 29:13).
We cannot know exactly how God will judge but the point is starkly made - if you see it and know it, you are responsible to trust and obey. Refusal to do either is a greater wickedness than the sins of Sodom. Every day we have many choices to make. The Lord knows what we do and why; He knows the reality of our faith in Him and He will call us to account one day. It is so dangerous to know enough and yet not believe.