My group found this question to be a bit confusing.
When you compare verse 20 that says “‘You are demon-possessed,’ the crowd answered. ‘Who is trying to kill you?'” to verse 25 that says “At that point some of the people of Jerusalem began to ask, ‘Isn’t this the man they are trying to kill?'” it’s clear that different groups know different things. The first comment appears to come from those who, like His family, had come to the festival from the countryside. But verse 25 indicates that the second comment was from those who live in Jerusalem, who have a better understanding of the situation.
It’s an interesting contrast that these two groups had such different understandings about the reality of Jesus’ life at this point. It helps explain the confusion that surrounded Him. It may also explain the reaction his brothers had at the beginning of the chapter. They probably had no idea that His life was being threatened. But those who lived in Jerusalem knew.