What were some of the reasons that the Catholic Church began to grow weaker during the Renaissance?

The failure of Catholic empires, the end of Crusades as well as the philosophical developments in the Renaissance weakened the Catholic Church's influence.

Explanation:

By the time of the Renaissance, any gains from the Crusades which propelled the Catholic Church to the height of its power had subsided and the Holy Roman Empire had lost its influence. Italy had become a merchant country of city states that increasingly became independent of religion.

the philosophical thought of the age argued for the divinity of humans and upholding the human spirit, as such, the influence of Catholic religion took a hit and people began to criticize it.