the first protestors were actually assorted sects that lost their internal, political battles within the larger organization and were then labeled heretics by the winning side. If the schism was large enough, it became a separate religious organization. The Roman Catholic Church in the west. The Coptic Church, the Eastern Orthodox - which then under went its own schisms based to the eastern remnant of the Roman Empire. this is very general, of course.

Within the western church, abuses of power got pretty flagrant & Martin Luther headed the first successful protest. And the Protestants have been squabbling and splintering ever since.

I would recommend reading Eric Flint's alternate reality series - Ring of Fire - if that kind of thing appeals to you.

For my part, the details about the religious aspects of the 30 years war was a flashback to what bored & pissed me in religion class.

My response to the Jesus freaks of the '60's & '70's and the born again Christians running today remains - Get a Life!