Emperors would confer titles and gifts to new rulers, but did not intervene in the internal affairs of Central Tibet.
The Emperor intervened and relieved Prié of his duties.
Faustus is really rubbing it in, when the Emperor intervenes.
Emperors had always intervened in ecclesiastical matters since the time of Constantine I. As Cyril Mango writes, That practice continued from beginning to end of the Iconoclast controversy and beyond, with some emperors enforcing iconoclasm, and two empresses regent enforcing the re-establishment of icon veneration.
People wanted the Emperor to intervene.
Despite potentially holding the balance of power between the two, Napoleon III kept France neutral; the French Emperor (like most of Europe) expected an Austrian victory, but could not intervene on Austria's side, as that would jeopardise France's relationship with Italy post-Risorgimento.
The Emperor could intervene.
While fighting for survival against the Islamic armies, the Empire was no longer able to provide the protection it had once offered to the Papacy; worse still, according to Thomas Woods, the Emperors "routinely intervened in the life of the Church in areas lying clearly beyond the state's competence".
The extent to which the Emperor could, for example, intervene on occasions of disputed or unclear succession was much debated on occasion - for example with the Lippe-Detmold inheritance crisis.