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 "for whose benefit?", is a Latin phrase which is still in use as a key forensic question in legal and police investigation: finding out who has a motive for a crime. It is an adage that is used either to suggest a hidden motive or to indicate that the party responsible for something may not be who it appears at first to be.
Institutions should limit how much their leaders are allowed to sip from the seductive chalice of power.