The two sides involved have VERY different versions of the history involved.
There is likely some untruth, and some truth, on BOTH sides. As is usual, whenever humans are involved, things get messy. Both sides have done some wrong things, and both sides have done some right things since the breakup of the Eastern and Western Churches.
Part of the problem was that the Roman Empire effectively split in two, with a Western Emperor and an Eastern Emperor. The Church officials tended to support THEIR civil authorities, and over time differences in opinions and practices led to a split.
In the earlier days of the Church, the Pope was NOT as decisive a leader as he later became. While technically, he may have had the inherent authority, they tended to utilize Church Councils for major decisions, and NOT make unilateral decisions that they then tried to impose on everyone.
It was the issue of the Filoque that really brought a lot of issues to their heads. The East simply could not accept the Filoque, the West insisted that all HAD to accept it.
The interesting thing is that most of the Eastern Catholic Churches DO NOT state the filoque in their version of the Creed, but state that the Holy Spirit proceeds from the Father (see this weeks “Our Sunday Visitor” for a more detailed explanation of this issue).
The bottom line that most divides the Orthodox from the Catholics is the issue of the Supremacy of the Pope. They see the Pope as “First among equals”, but NOT as THE ULTIMATE AUTHORITY AND LEADER.
Until, and unless, the Catholic Church can adopt that premise, there is virtually no hope of the majority of Orthodox joining back into one Universal and Catholic Church.
It is truly a shame, because the Catholic and orthodox Churches have so much more in common than they do in opposition. The Catholic Church accepts all Sacraments and Orders of the orthodox Churches as being valid in their entirety (sadly, not all Orthodox do the same with the Catholics), and our basic beliefs are essentially identical (with the one exception of the Holy Spirit proceeding either from the Father alone, or from both the Father and the Son)
The following is MY OPINION:
I believe that the leaders of BOTH sides are in a state of Mortal Sin, because their pride and human stupidity will not allow them to compromise, and rejoin what Christ wanted to never see sundered. Both sides could give, both could compromise, and bring those two great Christian Religions back together again. There has to be a compromise that both sides could live with, some “middle ground”.