Then people went out to see what had happened, and they came to Jesus and found the man from whom the demons had gone, sitting at the feet of Jesus, clothed and in his right mind, and they were afraid.
This response was partly due to the reputation of the wild man of the tombs, and partly due to the power of Jesus. We know the people of the Gerasenes had to deal with this demonized man in the past. They tried guarding him and shackling him with chains, only to have him break the bonds and run madly back to the desert tombs outside the city (see Luke 8:29). They kep their distance from him out of fear, making no more attempts to control his entrapped life by further bondage. They let the demons have him.
But here is this tormented man now clothed, delivered by Jesus, and in a civil frame of mind... and they are still very afraid. This time it is because of the change Jesus brought that saved this man and sent their pork futures plummeting over a cliff to drown in the lake (see Luke 8:33-34). The fear of the wild man has been replaced by the fear of the God man. But this is not righteous respect for the power of Jesus. They do not like what Jesus has done, because it has cost their city to see this man changed.
And so do many people react to the radical changes Jesus brings. They can't accept a new normal that is truly normal and righteous. That is what makes Jesus so controversial.