The New Day are just Two.
On Monday Night Raw, Kofi Kingston and Xavier Woods ousted Big E from the faction, NEW DAY! The event of a separation was determined that Big E was never there for the group after his neck injury. There was no possible reconciliation or finding a common goal to continue the 10 year journey that the faction had. Instead, Big E was left walking back to the locker room, alone and disappointed. In fact, it may be what Kofi and Xavier needed as they began to bond again.
Over time, members within a faction may develop divergent views on the best way to achieve their goals. This can lead to disagreements on strategy, tactics, or even the end goals themselves. If these differences become irreconcilable, a split may occur.
In essence, while factions are formed based on shared beliefs, human dynamics, conflicting interests, and external pressures can all lead to internal rifts, often prompting a separation as a way to preserve the integrity of the individuals or the group as a whole.