Have you never seen a tree that splits into two trunks?

The Schism of 1054 that split eastern and western practices was still a formal spilt from Western Christianity (i.e. Roman Catholicism) to recognize an equally long standing set of practices and traditions. There were other political factors that assisted the formal split and those do not negate the long standing traditions of the eastern church. I get it but it was still an ELI5 explanation.