>>42282818
Celestia orchestrated all of the friendship problems in order to keep the Element bearers sharp. If the EoH are Equestria's nuclear option, and only ponies that truly embody those qualities can wield them, then their bearers need to be kept in practice in upholding those qualities to ensure that Equestria is always protected. Celestia deliberately creates challenges for the Mane 6, often relating to their Element, so that they're always re-learning how best to embody that Element and thus staying qualified to wield it.