" Sacrosanctis was in fact the public face of a corporate conspiracy between the leading men of three powerful European families: the Medici (in the form of Pope Leo); Jakob Fugger, head of the Augsburg banking and mining dynasty and a man often said to have been the richest in human history; and Albert, archbishop of Mainz, a member of the politically influential Hohenzollern dynasty and (not coincidentally) the man to whom Luther mailed the first copy of his Theses.
The nature of the agreement between these three was broadly thus: Albert, who was already archbishop of Magdeburg, had been permitted by the pope to become archbishop of Mainz at the same time – which made him the most senior churchman in Germany, and meant he controlled two of the seven electoral votes which determined the identity of the German emperor. (His brother already controlled a third.) Vast fees were due to Rome as a tax on taking office as an archbishop – but Albert could afford these, thanks to a loan from Fugger, who advanced the money on the basis that he would have the Hohenzollern and their electoral votes in his pocket. Albert, for his part, promised Leo he would do all he could to make sure that German Christians bought as many indulgences as possible, partly because his share of the proceeds could repay his debt to Fugger and partly so that funds would flow rapidly to Leo in Rome for the completion of St Peter’s. For the parties involved this was a neat arrangement by which they all got what they wanted – so long as the faithful did their part and kept pumping money into pardons. "

― Dan Jones , Powers and Thrones: A New History of the Middle Ages