Why did attempts at reunion at the Council of Lyon in 1274 fail?

The attempts at reunion at the Second Council of Lyon in 1274 failed primarily because the initiative was a top-down political maneuver rather than a grassroots ecclesiastical movement.12

Emperor Michael VIII Palaeologus pursued the union to secure political and financial support from the papacy against the ambitions of Charles of Anjou, who sought to restore the Latin Empire in Constantinople. While the emperor’s delegates accepted papal primacy and the Filioque clause to satisfy Western demands, the agreement lacked support from the broader Orthodox Church.132

The union was viewed by the clergy and laity as a capitulation to the West, especially following the trauma of the Fourth Crusade in 1204, which had left deep-seated hostility toward the Latin Church. Consequently, the Greek clergy repudiated the union, and the Eastern churches ultimately refused to recognize the Council of Lyon as ecumenical. Upon the death of Michael VIII, an Orthodox council formally condemned the union in 1285.1234