Well, Calvin was the head of the church in the entire city of Geneva and wasn’t immoral....not every Pope has been immoral either.
But on the whole, I think you are right....the temptation for any man in power is great.
We are thankful that there are many men of God who have withstood the temptation presented by position and power.
That does not disprove the abnormality of the position.
And most truly godly and humble men will not allow themselves to be put there.
The emphasis in the NT is wholly on a plurality of leadership - not that of a single person. We find no man in the NT in that position, including James, Peter and Paul. To conclude they were in such a position requires a serious twisting of scripture and the inserting of imaginations that just are not there.
A plurality of leadership provides accountability that normally will keep an individual from exalting himself above others.