Answer:
A practice called simony, and the general corruption of the church entirely
Step-by-step explanation:
During the 1400s and 1500s, the catholic church was generally involved in large amounts of corruption. An example of this was basically buying your way out of purgatory, in which the church would sell things that basically made someone's family member get out of purgatory. This helped raise money for the catholic church, but simultaneously gave the church large amounts of criticism. These practices helped fund many theological buildings that are still in Vatican City today, such as St. Peter's Basilica. Martin Luther pointed these out, and many people agreed with him, mainly merchants. This is one reason why Martin Luther wrote his 95 theses.
Another practice was known as simony, which is the selling of theological positions. This was especially common in the HRE and papal states, and helped gain more money for the church. However, it also installed large amounts of corruption, as back then people saw the position of pope as a way to increase their political power as well as their countries. People were increasingly focused on financial gain rather than theological morals.