It did. Leo's tome was judged by the standard set by Cyril.
They were loyal to Dioscorus.
Leo followed Cyril, so we all follow Cyril.
Indeed; in all fairness to the Oriental Orthodox they were also faithful to St. Cyril; the tragedy at Chalcedon was a needless schism between two groups neither of which was Nestorian.
There are three apparent villains: Eutyches, who had lied to Pope Dioscorus of Alexandria, and had been anathematized by him by the time of Chalcedon, but his lie caused the disaster that was the Second Council of Ephesus, Ibas, a crypto-Nestorian who continued to sow division, and finally, Nestorius himself, who in exile, in his self-serving Bazaar of Heraclides, claimed that Chalcedon implemented precisely what he had been trying to implement, which assuming Nestorius was aware of what Chalcedon actually said, could only be regarded know is a false and intentionally divisive statement, since Chalcedon unlike Nestorius upheld the veneration of the Blessed Virgin Mary as Theotokos, whereas the entire Christological rabbit hole of Nestorianism was embarked upon due to Nestorius being a crypto-antidicomarian, opposed to the veneration of the Blessed Virgin Mary and scandalized by the phrase “Theotokos,” thus speculative theology by Theodore of Mopsuedtia was used heresiogenically in order to provide a Christological rationale for rejecting theotokos, through the hypostatic and indeed prosoponic division of the divinity and humanity of Christ.
Thus attempts by misguided Roman Catholics out of touch with the process of ecumenical reconciliation to claim Archbishop Leo (he was not styled Pope - this title was only used by the bishops of Antioch and would remain as such until the mid 6th century) acted with supposed Papal authority are historically incorrect, anachronistic, ignorant of the events that actually transpired at the council, and also rather blasse considering the tragedy of the EO-OO schism, something we are just now beginning to close the books on thanks to the efforts of the likes of Metropolitan Kallistos Ware, memory eternal, Metropolitan Hilarion Alfeyev, and other Orthodox bishops of IOTA:
What is IOTA?