There were multiple Popes in different areas. People use to buy higher-up jobs, the people who had these jobs didn't even do them. The pope would sell indulgences to people for money.
People say that Jesus walked on the stairs and when you go up the stairs they give indulgences to deceased people. Luther thought if this was true while going up the stairs, then remembered a Bible verse.
Diet of Worms
Luther the 95 Theses because he thought that selling indulgences was wrong and that people lived for God's grace.
By grace alone (Sola Gratia) Through faith alone (Sola Fide) In Christ alone (Solus Christus) According to sculpture alone (Sola Scriptura) For God's glory alone Soli Deo Gloria)
Luther said that he will not listen to the Popes or anybody and they can not use his words against him. "Here I stand. I cannot do otherwise."
While Luther was in hiding at the Wartburg Castle, he "grew his hair and beard" and called himself Junker Jörg (Knight George). Luther had put a task on himself to translate the New Testament from Greek to German.