Nothing. The insertion of the Filioque was not done properly, so the East had a good reason to complain; then the issues of church administration took over and the split solidified. There are several theological explanations of Filioque that are acceptable to both sides. It is not a theological dispute, although the Russians especially like to make it one, for reasons known to them.
Amusing that the Protestants in their ignorance of the Holy Scripture don't notice that the Eastern position is more scriptural and repeat the Latin creed.
But there's way more than just one issue. There are major ones that according to Rome, result in ex-communication and damnation for believing.
So they technically damn the EO for their disagreements with then turn around and claim they are *in communion* with all other rites, even after they damn them.
The great irony, and hypocrisy, is that in almost every other area, Catholics appeal to *official* Roman Catholic teaching and yet here, when it's convenient and necessary to present a united front, they ignore it.
Oooooo...you might want to follow up on some things like original sin, accepting the authority of the Pope, and who the Holy Spirit proceeded from (the Filioque). You make it sound so simple yet they left the Church.
It seems to me that if the Roman Catholic Church is teaching "infallible truths", then one has to conclude the Orthodox are wrong. You can't both be right. But I understand that in the Alice in Wonderland view of the Catholics, this makes perfect sense. Let me know when you get back together.
BTW-It doesn't surprise me that you would feel the Eastern position to be more scriptural. Undoubtedly part of the Neo-Palamism. Catholicism is abandoning ratioinal thought for mystical experience.