Discuss the decline of the Catholic Church during this period of history and the underlying causes of its decline

What will be an ideal response?

The growth of the European nation-states, whose political interests became independent of religion, contributed to the weakening of the Christian commonwealth. As Church and state competed for influence, two events damaged the prestige of the Catholic Church: the Avignon Papacy and the Great Schism. The term "Avignon Papacy" describes the relocation of the papacy from Rome to the city of Avignon in southern France. There, Avignon popes established a luxurious and powerful court, competed in prestige and political influence with the secular rulers of Europe. The Avignon popes used stringent (and occasionally corrupt) means to accomplish their purpose and their unsavory efforts at financial and political aggrandizement damaged the reputation of the Church.
The Great Schism occurred when the return of the papacy to Rome in 1377 was followed by a rift between French and Italian factions of the College of Cardinals, who elected two popes, one who ruled from Avignon, the other who ruled from Rome. This schism produced two conflicting claims to universal sovereignty and violent controversy within the Church. As each pope excommunicated the other, lay people questioned whether any Christian soul might enter Heaven and the very sanctity of the Holy Office was violated.