Do you know the saying “knowledge is power”? We think it's no big deal to read books in English. Yet during the Reformation, a single printing of the Bible in German led to huge changes.
Before the Reformation, most Bibles were in Latin. Only religious leaders could read Latin. So people had to rely on what the Catholic Church taught them about Christianity. The pope could decide what was true and what was false in religion.
When Luther printed the Bible in everyday German, he gave common people knowledge. That knowledge was power. People didn't have to rely as much on priests to explain Christianity. For example, was the pope following the Bible’s teachings? Were the priests? For the first time, people had the knowledge to think about religion for themselves.