Another answer from our community:
because despite leo's arguments many church leaders in esatern Europe most notably the byzantine patriarch michael cerularius refused to recognize the supremacy of the pope
The split between the Catholic west and the Orthodox east, which culminated in the Great Schism of 1054, was all about personal power and political opportunism. Since the second century, the Roman bishops had sought to establish supremacy over the Christian Church as a whole. Even in the west, and long after the split, successive popes sought to move power away from councils of bishops to the person of the pope.
The trigger for the schism was the insertion of the filioque clause into the Nicene Creed by Pope Leo IX, without prior agreement by a council of bishops. This clause was not so theologically significant in its own right, for the pope to risk a split in the Church nor for the eastern patriarch to play his part in the split. However, Pope Leo IX sent envoys with the authority to excommunicate Patriarch Michael I, if he did not submit. Michael would have excommunicated Leo in turn, but the pope being already dead, had to content himself with excommunicating the envoys.
There were attempts at reconciliation and the Churches came close to being reunited in 1274 and in 1439, but the schism eventually became permanent.
Because he wouldn't recognize his authority as a pope.
If the place is Constantinople then the answer is: because he wouldn't recognize his authority as a pope.
The Eastern Orthodox Church.
Pope Benedict IX
The last to be elected when not yet a bishop was Pope Gregory XVI in 1831, and the last to be elected when not even a priest was Pope Leo X in 1513.
Patriarch Leo of Constantinople died in 1143.
I think pope Leo I
Two Popes that declared the other to be a false pope, excommunicating each other.French pope lived in Avignon and the other Italian pope lived in Rome, this began the division between the ChurchesA:The Council of Nicaea, called by the Roman Emperor Constantine in 325, decided that Christianity in the Roman Empire would be led by four senior bishops or Metropolitans representing Rome, Alexandria, Antioch and Jerusalem. The Council also made provision for Constantinople and Carthage, where Metropolitans were subsequently appointed, although the role was short-lived in Carthage. Thus, religious authorities in the mainly Greek-speaking eastern regions held that the bishop of Rome was one among equals. However, the bishop of Rome, designated in the west as the Pope, insisted that he had greater authority than the other Metropolitans. Gradually, differences built up until, in 1054, Pope Leo IX insisted on the right to make a change to the Nicene Creed, on his own and apart from an Ecumenical Council. The Great Schism resulted when Pope Leo IX sent envoys who purported to excommunicate Patriarch Michael I, who in turn excommunicated the envoys, Leo having died just prior to this meeting.
Two Popes that declared the other to be a false pope, excommunicating each other.French pope lived in Avignon and the other Italian pope lived in Rome, this began the division between the ChurchesA:The Council of Nicaea, called by the Roman Emperor Constantine in 325, decided that Christianity in the Roman Empire would be led by four senior bishops or Metropolitans representing Rome, Alexandria, Antioch and Jerusalem. The Council also made provision for Constantinople and Carthage, where Metropolitans were subsequently appointed, although the role was short-lived in Carthage. Thus, religious authorities in the mainly Greek-speaking eastern regions held that the bishop of Rome was one among equals. However, the bishop of Rome, designated in the west as the Pope, insisted that he had greater authority than the other Metropolitans. Gradually, differences built up until, in 1054, Pope Leo IX insisted on the right to make a change to the Nicene Creed, on his own and apart from an Ecumenical Council. The Great Schism resulted when Pope Leo IX sent envoys who purported to excommunicate Patriarch Michael I, who in turn excommunicated the envoys, Leo having died just prior to this meeting.
because he decided to start a fake religion
Pope Leo XIII was the pope in 1896. He was pope from 1878 to 1903.
Pope Leo became the Pope in 1513, his name also changed from Giovanni di Lorenzo de' Medici to Pope Leo.