There’s a backstory to the commencement of the Protestant Reformation that, while it runs all the way back to the time of the post-apostolic fathers and following them, the events between the close of the New Testament and the Council of Nicaea. There were more immediate events that showed the obvious need to reform Catholicism. So, this is to discuss those more immediate events.
The Catholic Church completely dominated Western Europe, and the extent of that domination was unlimited. Their authority reached into politics, government, education, religion, and economics. The Roman Catholic Church was the single largest landowner in the Western Europe of the Middle Ages.
In 1302, the pope issued an edict stating that salvation outside the Catholic Church was simply not possible and that all the authority in the Catholic Church was vested in the Pope. Then, 45 years later, in 1347, the Black Death began in Europe, and 25 million people died in a period of four years. Society, under the complete control of the Catholic Church, was shaky enough before that, but following the Black Death, there were a lot of people whose faith had been shattered.
Devout believers had been calling upon God, getting blessings from the Bishops, doing what the priests could do in order to save the lives of people. They all failed, and there were many who began to rethink the order of things. They had called upon Catholic help in their distress, and Catholic help had been given, but it was ineffective.
Then, shortly after this, for a period of 31 years, there was an internal split in the Catholic Church. There were two popes claiming to be the exclusive holder of the keys from Peter. One of them in Avignon and another claiming the same thing in Rome. Then, a third Pope contended he had the keys from Saint Peter. From 1409 to 1415, there was a three-way fight between Gregory XII, Benedict XIII, and Alexander V over who held primacy and could claim to be the one exclusive holder of all authority in the Catholic Church.
Well, it doesn’t take a genius to figure out that in those circumstances, doubts about the authority of Catholicism multiplied. People living at the time witnessed a spectacle that made them wonder if Catholicism could survive the crises that had compounded them. And so, that historical prelude resulted in widespread questioning and doubting about the claims of the Catholic Church to be God’s sole representative for salvation on Earth.
Johannes Huss in Czechoslovakia and Savonarola in Florence spoke up. They were both regarded as rebellious doubters of Catholicism, and both of them were burned as martyrs because of their doubt. Catholicism was not going to share power willingly. These two martyrs were in recent memory when Martin Luther lived. Their deaths go to show that strongly held convictions were necessary for someone to muster the courage Martin Luther summoned to question the Roman Church. His questioning resulted in what we now refer to as the Protestant Reformation. When he protested against the church, recent history proved it was life-threatening to come out in opposition to Rome. There are few men who would risk being burned at the stake to voice criticism against a powerful but corrupt religious hierarchy.