Final answer:
Luther grew increasingly angry over the Catholic Church's sale of indulgences, Church taxation, and the use of Latin in Mass, which led to the Protestant Reformation.
Step-by-step explanation:
Martin Luther became increasingly angry about several practices of the Catholic Church, particularly the sale of indulgences. Indulgences were considered tickets that reduced the time one spent in purgatory and were being sold to fund the construction of St.
Peter's Basilica. Luther's theological disagreement with this practice led to his critical Ninety-five Theses, which he posted on the door of the castle church at Wittenberg, challenging the idea that salvation could be purchased and criticizing the Church's greed and abuse of power.
Luther also took issue with the Church's taxation of ordinary Germans and the use of Latin for Mass, which was not understood by the majority of German Catholics.
His beliefs, condemned by Pope Leo X, eventually resulted in his excommunication and gave rise to Protestantism, significantly challenging the authority of the Pope and the Catholic Church's teachings on salvation and good works. The spread of Luther's ideas was facilitated by the printing press, allowing them to quickly reach a wider audience.