Why did the uniting churches split?

Question

The uniting church history, not the current uniting church

Answer 1

If I understand correctly, you're referring to the split between the churches in Western Europe and those of the East.

The split occurred over the celebration of Easter.  The West, which ultimately became known as the Roman rite churches, had one way of calculating the date for the celebration of Easter, while the churches of the Eastern rite (such as the various Orthodox churches, i.e., Greek Orthodox, Russian Orthodox, Serbian Orthodox, etc.) determined the date of Easter by when Passover occurred.

Interestingly, there were other churches in the West who were also not in step with the Roman rite, notably the Celtic churches in what is now Ireland.  At the Synod of Whitby, they agreed to conform to the Roman practice.

This break is often referred to as The Great Schism.

Answer 2

Power and property.  The usual Christian ideals.