Ahh, The Great Schism...
Many latter day armchair historians like to think the theological issues were secondary and the main driven was East-West hatred...but that is latter day socialist dreck (culminating in present day woke garbage) that seeks to promote cultural differences like socialists all like to do as a means of legitimizing their fringe beliefs and mainstreaming their powerbase...
It was not a Pope Leo IX vs Patriarch of Constantinople (or See of Constantinople) Michael Cerularius cage match.
Things came to a head in 1054 after a series of councils discussing theological issues and the primacy of the Bishops of the Churches.
A big point of contention was over the Trinity...the Latin use of filoque in the Nicene Creed for from whence the Holy Spirit flows...and it seems kind of odd for a "Christian" to demote Jesus as the Eastern Orthodox did, but it was a big deal to these early church leaders...as was using unleavened bread in Eucharist...and relatively lesser differences on original sin etc...and yes, governance.
The Bishop of Constantinople has an honorary title of First Among Equals but in Orthodox structure the Bishops of the key churches (and in their view) including the Bishop of Rome (aka The Pope) are all equals...(and interestingly the honorific First Among Equals was also used by the East for the Bishop of Rome pre-Schism)...the 5 Patriarchs were - Rome, Constantinople, Antioch, Jerusalem & Alexandria... The East saw St.Peter as the first Bishop of Antioch, at this time not even the West saw him as the First Bishop of Rome...but around the 3rd century it became popular in the West to see him as First Pope, and many see the scripture where Jesus says to Peter he shall be the rock upon which he would build his church and the fact that he was martyred in Rome as support of that even if the title had not yet existed. It also shows the centralized versus decentralized view of East and West at the time.
Anyway, excommunications ensued both directions, each went their separate ways and not until the 4th Crusade did some ill-advised morons from Europe see an opportunity to plunder the wealth of the Eastern Empire than be slaughtered in the dust of the Holy Land fighting howling Muslim hordes...
If some are butthurt over that, well...that's their problem. Vatican II saw reconciliation and the lifting of each others excommunication decrees. Everybody is getting along now...nobody needs to be an asshole. Well, Z...but that's his fricken problem, not mine/ours/yours.
