look at martin luther who thought that salvation was acheived through faith, and not through the selling of indulgences or good works

he broke away from the catholic church and started Lutheranism

and then you have John Calvin who came up with predestination

which is the belief that God has chosen from the beginning whether you were going to be saved or not. He started Calvinism. Before the protestant reformation, there basically was only catholicism, and no other forms of Christianity, you were either catholic, or, the king/queen would have you executed

guys like martin luther and john Calvin revolutionized the world

with their beliefs.