In the name of the Pope, give us half of your earnings!
During the Middle Ages, the Catholic Church was the most powerful religious stance in the area.
Them being so powerful, they needed resources for both the church, and their greed. From animals to money, the \y had asked for anything the people could give.
Most of the time it was the Pope that had gotten most of the riches. They had no worries about any revolution against them, seeing as a lot of people were dependent on the Church.
After the creation of the printing press, books became more accessible which allowed for more people to become literate. This also allowed Bibles to become more popular, which was able to show people the lessons of Christianity that the Catholic Church did not teach them.
Not much later, Martin Luther had enough of the Church. And posted a 95 argument filled list of what was wrong with the Catholic Church. He made sure to post it everywhere to show the public that change was needed.
Eventually, Martin created his ow form of Christianity, and then the First Protestant Church was created. Not much was different between the two. But from then on, more and more people had started following Martin's way of Christianity.