For early modern rulers, the Church's power was a two-way street. Being allied with the Church gave them the protection of God, and often some financial advantages, but it went along with needing to do what the church wanted. The church had the power to designate bishops, levy taxes, and control marriages even within a ruler's kingdom.

Luther, on the other hand, said that temporal rulers (princes, kings, etc) should be able to rule their lands without any interference from the church, and that was very attractive to many rulers at the time.