Why did some of the scribes think that Jesus was blaspheming God?

Some of the scribes thought that Jesus was blaspheming God because Jesus told the paralyzed man that his sins were forgiven.

Why did Jesus say he had told the paralytic that his sins were forgiven, instead of telling him to get up and walk?

Jesus had told the paralytic that his sins were forgiven to demonstrate that he had authority on earth to forgive sins.