The events that set the stage were mainly events of unfairness that were present in the Church at that moment, as it had been for years. His superior, Albert, archbishop of Mainz, struggled to pay a large sum for the rebuilding of St. Peter's Basilica in Rome. Albert received permission to do special plenary indulgence such as remission from the temporal punishment of sin. Martin Luther, indignant from such wrote to Albert complaining about such a sale. He enclosed with the letter his "Disputation of Martin Luther on the Power and Efficacy of Indulgences", which later became the Ninety-five Theses that were so widely spread. I one of those theses, he asks why couldn't the Pope, so wealthy as it was, pay for the rebuilding instead of asking such sacrifices from the poor and needy believers.
Later he went on to criticise much more, always with his emphasis on the centrality of all powers in the Pope. Later he was excommunicated.