Korazin and Bethsaida were only an hour’s walk from Jesus hometown of Capernaum. They were Jewish towns filled with Torah abiding Jews. So how could these towns receive a harsher judgement than the idol worshipping Gentile towns of Tyre and Sidon? This follows on from Jesus’ teaching regarding the difference between how the world and how God judged John the Baptist. Jesus now reveals another another important aspect of judgement: We are judged on the degree of revelation we possess.
These towns and their inhabitants had greater insight into the Kingdom of God than Tyre and Sidon, therefore the standard by which they were judged will be much higher. It is like the discipline of children: a 7 year old will receive a harsher judgement than a 3 year old for the same infraction because ‘they should have known better’. It is very sobering to think that Sodom which was destroyed will be better off on Judgement Day then Capernaum.

“And to you Capernaum; do you think you will be honoured in heaven? No, you won’t. You will go down to Sheol. For if the same miracles you witnessed had been done in Sodom, it would still be here today. I tell you the truth, even Sodom will be better off on judgment day than you.” TJG 10:48