True, Cesare became Captain-General of the Church in his dead brother's place; but for that his brother's death was not necessary.

Gandia had neither the will nor the intellect to undertake the things that awaited Cesare.

He was a soft-natured, pleasure-loving youth, whose way of life was already mapped out for him.
His place was at Gandia, in Spain, and, whilst he might have continued lord of all the possessions that were his, it would have been Cesare's to become Duke of Valentinois, and to have made himself master of Romagna, precisely as he did.
In conclusion, Gandia's death no more advanced, than his life could have impeded, the career which Cesare afterwards made his own, and to say that Cesare murdered him to supplant him is to set up a theory which the subsequent facts of Cesare's life will nowise justify.
It is idle of Gregorovius to say that the logic of the crime is inexorable--in its assigning the guilt to Cesare--fatuous of him to suppose that, as he claims, he has definitely proved Cesare to be his brother's murderer.
There is much against Cesare Borgia, but it never has been proved, and never will be proved, that he was a fratricide.

Indeed the few really known facts of the murder all point to a very different conclusion--a conclusion more or less obvious, which has been discarded, presumably for no better reason than because it was obvious.
Where was all this need to go so far afield in quest of a probable murderer imbued with political motives?
Where the need to accuse in turn every enemy that Gandia could possibly possess before finally fastening upon his own brother?
Certain evidence is afforded by the known facts of the case, scant as they are.

It may not amount to much, but at least it is sufficient to warrant a plausible conclusion, and there is no justification for discarding it in favour of something for which not a particle of evidence is forthcoming.
There is, first of all, the man in the mask to be accounted for.