How did Catholic Church change during the Middle Ages?like how did corruption lead to middle ages

During the middle ages, the Catholic Church began to become more and more involved in secular government. They began to play a large role, especially in organizing government participation in the Crusades and trying to enforce to "Peace of the Church", the goal of which was to limit the ways and means secular governments could wage war against each other. The church also became the center for education because there were so few secular schools. However, as the power of the Church grew, so did corruption and greed. The church began to tax secular leaders at higher and higher rates. One of the most egregious practices was that of issuing "Indulgences", a document sold by the Catholic Church which, they said, paid for sins committed by the buyer or others. The indulgences were issued to pay for large building projects and an increasing number of bureaucrats in Rome. Tired of paying for rich living in Rome, many secular leaders were ready for a change. Thus, when Martin Luther posted his arguments against indulgences on the door of Wittenburg University, he launched the reformation, designed originally to reform the Catholic Church but in the end it split the church and ushered in the Protestant Reformation.