If the Catholic Church was so powerful, why did the Protestant Reformation take place?

The Catholic Church had traditionally been the dominant socio-political and religious force in Europe in the centuries leading up to the Protestant Reformation: popes were some of the most influential figures of the medieval period, regional monarchs were expected to answer to the papacy, and much of the laity still feared divine retribution - and that the Catholic Church were God's representatives on Earth and their only chance at salvation. These factors meant that Christianity was undoubtedly an all-encompassing part of the European populations' life in the years leading up to Luther's protest in 1517, but despite the dominance of the church several challenges to papal authority had begun to surface. There were numerous examples of Popes, bishops and clergymen openly behaving in an ungodly manner, unbefitting of religious and spiritual leaders. Popes such as Benedict IX and Alexander VI had begun to be known for their decadence and hypocrisy. Academics, most famously Erasmus, had begun satirical attacks on papal institutions, and the Great Western schism had divided Europe which created political and regional enemies to Rome. This had left the Catholic Church more vulnerable than it had ever been to criticism, and popular revolt, and it was in this environment that Luther emerged and gained a following.