"This death is very harmful to the King of France, to all Italy, and chiefly to the Pope, who is thereby deprived of 40,000 ducats yearly, which was paid him by his [Djem's] brother for his custody.

And the king showed himself greatly grieved by this death, and it was suspected that the Pope had poisoned him, which, however, was not to be believed, as it would have been to his own loss." Just so--to his own infinite loss, not only of the 40,000 ducats yearly, but of the hold which the custody of Djem gave him upon the Turks.
The reason assigned by those who charged Alexander with this crime was the bribe of 300,000 ducats offered by Bajezet in the intercepted letter.

The offer--which, incidentally, had never reached the Pope--was instantly taken as proof of its acceptance--a singular case of making cause follow upon effect, a method all too prevalent with the Borgian chroniclers.

Moreover, they entirely overlooked the circumstance that, for Djem's death in the hands of France, the Pope could make no claim upon Bajazet.
Finally--though the danger be incurred of becoming tedious upon this point--they also forgot that, years before, Bajazet had offered such bribes to Charles for the life of Djem as had caused the Knights of Rhodes to remove the Turk from French keeping.

Upon that circumstance they might, had it sorted with their inclinations, have set up a stronger case of poisoning against Charles than against the Pope, and they would not have been put to the necessity of inventing a toxin that never had place in any earthly pharmacopoeia.
It is not, by this, suggested that there is any shadow of a case against Charles.