My friend, The church was always important for the Holy Roman Empire, because having control on the church means having control over any other Christian nation, basically, controlling all Europe; also, in the Matin Luther Reforms, the Lutheran nations loosed authority over the church and the pope, and considering that Matin Luther was a German, it was a hard hit on the Empire. And yes, bishops had very real political power even now, as surprising as it sound, of course, less than then but still with power; the difference, is that the church told the people what was right and what was wrong, and such, it was a way of imposing your rule without having to proclaim actual law. Just think about it "if you don't do this you are going to hell" doing what? what The Emperor don't wants you to do.