Who founded orthodox Christianity?

Answer 1

The Orthodox Church, as we know it today, originated by accident to some extent, when the unified Christian Church split in 1054, to form the Catholic Church in the west and the Orthodox Church in the east. Pope Leo IX sent Cardinal Humbert as legate to Constantinople with instructions to excommunicate Patriarch Michael if he did not accede to certain demands. This act led to the Great Schism of 1054 and the formation of the Roman Catholic Church and the Greek Orthodox Church that we know today. It could therefore be said that Leo IX started Orthodox Christianity.
However, it was the direct act of Humbert in purporting to excommunicate Michael that led to the split. Michael was unable to excommunicate Leo in retaliation, as Leo had already died at the time of this event, so Michael had to satisfy himself with excommunicating the legate himself. As Leo was no longer alive, Humbert could have stayed his hand until a new pope was elected, and by not doing so was also responsible for the Schism and the formation of the two Churches out of the former unified Christian Church. In all of this, Patriarch Michael also bears some responsibility, being partly responsible for the outcome, although his hand was forced.

No one person was responsible for the East-West Schism and the separation of the Roman and Greek Churches, but we can attribute the start of the modern Orthodox Christianity to Pope Leo IX, Cardinal Humbert and Patriarch Michael.