From what I've read, it was a mutual excommunication. Both sides simultaneously split from the other, so it's not right to say the EO split from the RCC or the RCC split from the EO. They just split.
THe reason is because the Roman Catholic changed practice and doctrines first lets look at practice kneeling on Sunday mandatory priestly celibacy are banned by the first through 6Th ecumenical councils- nothing changed in the 7Th. Same with starting Lent on wen day opposed to monday the canons do allow for devorce in some cases- estream like adultury you can ask the Copts and Syriacs about that. Next doxtriens there is first the creed the creed was not supposed to be changed- you did- in oppition to the eccuminical agreements you canged the meaning by adding the word filioque.
why does the Eastern Orthodox Church believe that the Catholic Church split off from
