The printing press was an efficient way to spread (most importantly) the Bible to many people at a lower cost. Before, only nobles could afford bibles because each one was handwritten over the course of 5 years. Because of that, priests took advantage of people’s illiteracy to tell lies about the religion. One of the most famous examples of these was the selling of tickets that supposedly “forgave sins”. The priests got rich off of that, but now that people’s literacy rate went up, they could read the Bible and stand up to say that that was wrong because it wasn’t in the Bible.