It says, "princes of darkness"

Where in Scripture is that equated with humans?

What does Scripture say about what are the "princes of darkness"?

Now, could many-to-most of the Cardinals have actually become possessed or were already under the influence of the demons - yes.

But again you are stretching here and trying to weave;

1) A Masonic prophecy.

2) A dubious 3rd Secret of Fatima from a untrustworthy source.

3) Fr. Palau's visions that he handed to Pope Pius IX.

Which, of all three it is only number 3 that really merits any trust...

So trying to weave them together is just to tie yourself in knots I think.

If you actually start to delve into that 2000 page beast of Fr. Palau's work you will see that so much of his fight was centered on fighting the actual demonic through exorcisms of actual demons, and he explains that why his visions will come to pass is because all the devils have been slowly loosed from hell and returned after they were cast out by Christ, the Apostles, the Fathers, etc. They started to return because the few that were left were allowed to remain due to the negligence of the office of exorcist, they caused ever increasing damage and aided other demons in getting released from the pit as a punishment for sins and negligence. Palau was censured by his own bishop (who seemed to have been diabolically influenced) from performing exorcisms. He was trying to warn Pius IX about what needed to be done. Fr. Palau was exiled by the Masons (who he openly opposed) to an island of the coast of Spain/Portugal. From there he would often life in solitude in a cave on the mountain and that is were he heard this voice speaking to him for 20 years. He seems to have been gifted with seeing angelic and demonic spirits at many and various times. He was also highly sensitive to the spiritual and could sense the presence of evil. He actually does seem like another very holy priest like Padre Pio. The fake Church considers him a Blessed (though that means little to me).