"...when the Church of Rome held tyrannical sway over all of Christendom."

That was never true actually, even setting aside that rather polemical terminology. "Christendom" covers the Eastern Church as well as the Western.

Which comes first the chicken or the egg? Having a pseudo-religiuous excuse for wiping out your debts by killing the person to whom you owe money, for example, must have been very convenient at times. When diverting a mob to a scapegoat so that they leave your property alone, it comes in handy too.