By the 9th and 10th centurys the church had gradually become more and more controlled by the laity, who were the common non ordained people. Dukes and Lords often appointed bishops and abbots of monasteries, and if they built a monastery they considered it their property. Aristocratic families in Rome jockeyed for control over the papacy, which lead to some despicable popes such as pope John the 12th who toasted to the devil. After this the Holy Roman Emperor king of what is now Germany appointed the popes to avoid this. When pope St Leo the 9th began his papacy he began what is called moderate reform. He did away with heresy such as simony and clerical marriage but he did not go to the root of the problem which was laity appointing church officials. Instead he just thought that the laity should make sure to appoint good officials. But he did set up the system in which a college of cardinals appoints the pope which is still used to this day.
When pope St Gregory the 7th was appointed pope he realized the reason that none of his reform bills were working was because he could not appoint his own officials to carry them out. He abolished laity investiture which is where the king would invest a bishop when they were ordained with the symbols of temporal authority but they would also invest them with the symbols of spiritual authority which should not come from a king. This was bad for the church since a non ordained figure was investing the bishops with spiritual authority. But Henry the 4th king and Holy Roman Emperor of Germany persisted in doing this stating that it was a tradition even though it was an immoral one. This lead to pope Gregory excommunicating the king. Since this meant that all of his nobles would not listen to and rebel against him, he traveled to Canossa ,where the pope was staying, and waited three days in the snow to see the pope. Only after this the pope saw him and after the meeting the pope lifted Henry’s excommunication. Unfortunately directly after this Henry continued to invest bishops. The pope excommunicated him again but Henry this time exiled the pope from Rome where Gregory died in exile saying,” I have loved justice and hated iniquity, therefore I die in exile.” But soon after in 1122 the concordat of worms was signed mostly in the churchs favor and making laity investiture illegal.