The pope’s affirmation of the council was necessary (even if most Emperors were more interested in unification of the empire at the expense of orthodoxy), case in point, Pope Vigilius’s captivity by Pope Justinian in order to confirm the decrees of Constantinople II, i.e., you do not imprison a pope for 10 years without believing that said pope is crucial to the ratification of conciliar decisions. As before I would like to quote a previous post of mine concerning this:
forums.catholic-questions.org/showthread.php?p=6955441#post6955441
Your timeline is wrong. Vigilius was held in captivity for around two years at the most after the Second Council of Constantinople, not for ten years, and he was even held in captivity for at least one year after he had already recanted of his earlier decisions and approved of the Council.
Vigilius’ goal was to secure military aid for the city of Rome. Justinian wished to condemn the three chapters, something which Vigilius agreed to do. However, when Justinian convened the Second Council of Constantinople some time in mid 553, Vigilius refused to participate, because Justinian in convening the council had breached an agreement between the two of them. Justinian proceeded to hold the council without Vigilius. Under pressure from the Council, Vigilius, with a small gathering of sixteen other bishops who supported his cause, drafted his document, the First
Constitutum in which he defended the persons of Theodore of Mopsuestia and the writings of Theodoret and the Letter of Ibas, and forbade anybody from making a different judgment with the ‘authority of the Apostolic See’.
Upon receiving this *Constitutum *, Justinian presented to the Council several letters in which Vigilius had privately agreed to condemn the Three Chapters, causing Vigilius to appear duplicitous, sealing Vigilius’ fate. They struck him from the diptychs in the seventh session and in the eighth session made a judgment that the person of Theodore of Mopsuestia and the Three Chapters should all be anathematized, along with those who defended them. Vigilius was then held in captivity (some sources like the ones used for the Catholic Encyclopedia Article on the Second Council of Constantinople seem to indicate that he was sent into exile). On the eighth day of December in the year 533 wrote a letter to the Archbishop of Constantinople, Eutychus, in which he withdrew his First
Constitutum. He then wrote a Second
Constitutum, some time in February of 554, in which he promulgated the decisions of the council in the West (several sees in the West immediately went into schism upon receiving this Second
Constitutum, claiming that Vigilius and the East had abandoned the true faith of Chalcedon). Only in the year 555 (over one year after approving of the Council’s decisions) was Vigilius allowed to return to Rome (but he died on the way home).
If they imprisoned/exiled Vigilius because they needed his approval, as you claim, then why did he remain imprisoned for one year after approving of the Council’s decisions? Furthermore, if imprisoning Vigilius is proof that they needed his approval, does that mean that they needed the approval of Nestorius, who was similarly exiled? And why did the council feel free to contradict the pope, who had declared in his First
Constitutum that any declaration contrary to his would be nullified by the authority of the Apostolic See? Your interpretation of the Second Council of Constantinople leaves a few questions unanswered.