The priests played an important role in Sumerian city-states because the Sumerians believed that priests were the only ones capable of communicating with the gods and ensuring the prosperity of the city. This belief was a central aspect of Sumerian religion, and as a result, priests were revered and held high positions in society. In order to get the answer to this question, one should look for information about the role of priests in Sumerian society and their connection to religious practices and beliefs. This can be done by consulting reliable sources such as history books, scholarly articles, or reputable websites that provide information about ancient Mesopotamian civilizations.