Sedes are fond of citing Bellarmine and occasionally, Cajetan, to support their novel theories. Phillip Campbell has a good article here explaining why this is a problem.
The article argues that sedevacantists misinterpret Cajetan’s views on removing a pope and can’t use his arguments to justify their stance. Cajetan, a 16th-century theologian, indeed discussed the removal of a pope but strictly under the context of heresy, seeing the pope’s authority as directly instituted by Christ, not delegated by the Church. His unique stance was that in cases other than heresy, the faithful should resort to prayer for divine intervention rather than seek human legal mechanisms for removal.
The Conciliarists of his time mocked Cajetan for believing in prayer just as the sedes today mock Catholics for begging God for mercy from evil prelates. This was his response:
It does not follow from the fact that the Church has not been granted the power to depose by human provision that it has not been granted [any] power to depose a pope; for it does so unfailingly by another means, namely, by persevering in prayer.
…Each polity, whether civil or ecclesiastical, can depose one who rules it tyrannically, but in different ways—thr civil one, being perfect and free, by means of power and by human provision, the ecclesiastical, however, by means of the Father’s own power, by perseverance in prayer when it is truly necessary. This mode, more excellent and unable to err as the former can, is better, and, therefore, the ecclesiastical commonwealth is no less well but better provided for than the civil in regard to the way of ridding itself of an evil minister.
…There was not a more opportune remedy by human provision than the Church’s persevering prayer. First, because human provision can fail, since, indeed, “the thoughts of mortal men are fearful, and our counsels uncertain” [Wis. 9:14]; the Church’s persevering prayer, however, cannot fail. We might depose when it is unnecessary, neither foreseeing the future nor scrutinizing what is hidden. The Church’s persevering prayer, however, would not depose when it is unnecessary, because the good Lord denies what we wish so that He may give us what we prefer.
Read it all here.