They were afraid. The wall was a major step in Judah’s ascension to nationhood. Other nations saw that as a threat. Also, the neighbors saw the great accomplishment done in so short a time, and “perceived that this work was wrought of our God.” (KJV, Nehemiah 6:16) That being said, the Jewish people were considered still to be vassals of Persia. They were expected to give taxes and tribute to the king of Persia.