Interesting. How exactly, did Pope Pius XII "hold the fate of millions of Jews in his hands"?
Do you honestly think that a formal, by-name excommunication of Hitler and his minions, together with some sort of ringing denunciation, would have saved "millions of Jews"?
That's the most the Pope could have done publicly.
Because I don't honestly think it would have accomplished anything (good) except to justify Pius to a few more historians. An equal number of historians would have condemned him for the resulting more vicious persecutions of Jews and Catholics, as well as castigating him as a fool for thinking papers in Latin with pretty wax seals would have stopped Hitler.
As far as saving Jews privately, saving _millions_ of Jews simply wasn't possible logistically. As it is, 860,000 were saved, some by being issued fake baptismal certificates, some by being hidden in the Pope's own palace at Castel Gandolfo, some by being hidden in other religious houses and facilities.
Would the Pope have the power over members of his church to demand that those members take a specific action? For example, RC's are supposed to support Pro Life policies and politicians. Could the Pope demand all RC's support the pro life politicians or be excommunicated?
That you even ask that question is pathetic.