The Pope did actually die of disappointed fury because peace had been restored to the country he had mangled for the sake of a favorite nephew.
[1] This phrase requires support.

Infessura (loc.cit.p.

1941) relates the savage pleasure with which Sixtus watched a combat 'a steccato chiuso.' Hearing that a duel to the death was to be fought by two bands of his body-guard, he told them to choose the Piazza of S.Peter for their rendezvous.

Then he appeared at a window, blessed the combatants, and crossed himself as a signal for the battle to begin.

We who think the ring, the cockpit, and the bullfight barbarous, should study Pollajuolo's engraving in order to imagine the horrors of a duel 'a steccato chiuso.' Of the inclination of Sixtus to sensuality, Infessura writes: 'Hic, ut fertur vulgo, et experientia demonstravit, puerorum amator et sodomita fuit.' After mentioning the Riarii and a barber's son, aged twelve, he goes on: 'taceo nunc alia, quae circa hoc possent recitari, quia visa sunt de continuo.' It was not, perhaps, a wholly Protestant calumny which accused Sixtus of granting private indulgences for the commission of abominable crimes in certain seasons of the year.
The crime of Sixtus which most vividly paints the corruption of the Papacy in his age remains still to be told.