I cannot accept your canon that we are to judge Pope and King unlike other men, with a favorable presumption that they did no wrong. If there is any presumption it is the other way against holders of power, increasing as the power increases. Historic responsibility has to make up for the want of legal responsibility. Power tends to corrupt and absolute power corrupts absolutely. Great men are almost always bad men, even when they exercise influence and not authority: still more when you superadd the tendency or the certainty of corruption by authority. There is no worse heresy than that the office sanctifies the holder of it.
It is said that power corrupts, but actually it's more true that power attracts the corruptible.
Cui bono?, literally "to whom is it a benefit?", is a Latin phrase about identifying crime suspects. It expresses the utilitarian view that crimes usually benefit their perpetrators, especially financially.
Institutions should limit how much their leaders are allowed to sip from the seductive chalice of power.