Answer
Mu'awiya, the first Umayyad caliph, is credited with transforming the office of the caliphate into a kingship. Prior to Mu'awiya's reign, the caliphs were elected by a council of Muslim leaders. However, Mu'awiya established a hereditary monarchy, passing the caliphate to his son, Yazid I. This change marked a significant departure from the original Islamic caliphate, which was intended to be a religious office rather than a hereditary monarchy.