Which event arguably prepared the ground for the Protestant Reformation in the 16th century?

The destabilization of the institution of the papacy in the 14th and 15th centuries is a foundational event that set the stage for the Protestant Reformation. During this period, papal authority and influence were significantly weakened due to various factors, including internal conflicts, such as the Avignon Papacy and the Great Schism, which resulted in multiple claimants to the papal throne. This fragmentation of authority undermined the Church's ability to maintain control over Christian doctrine and fostered a climate of discontent among the laity and clergy alike.

Additionally, the growing skepticism towards the Church's leadership was further exacerbated by calls for reform from within the church, as many individuals sought to address the moral and ethical decay associated with the papacy and the clergy. Such an environment of questioning and critique directly contributed to the emergence of Reformation thinkers, like Martin Luther and John Calvin, who challenged the Church's teachings and practices. Thus, this destabilization created an opportunity for new religious ideas to flourish, allowing the Protestant Reformation to gain momentum and appeal among various populations disillusioned with the established Church.