>>18102610
>>18102612
Leo I genuinely believed he had universal authority and tried to veto Canon 28, raising Constantinople as New Rome and equal to the See of Rome, but his veto was basically ignored. But on the other hand, Gregory I called out the Patriarch of Constantinople at the time for trying to claim he had universal authority and could oust bishops outside of his jursidiction. Pic related.
So the answer is "it's complicated" but basically more and more popes started supporting it as time went on. Up to the point where it's like "well the Vatican is too big to fail, why would any pope concede his supreme authority now?" Admitting to nearly a millennium of error collapses the whole western church. In a similar reason to why the King of Saudi Arabia couldn't possibly apostatize.