Why was Philip II Augustus crowned at Reims in 1179 before his father died?

Philip II Augustus was crowned at Reims on November 1, 1179, because his father, Louis VII, had fallen mortally ill. The coronation was intended to associate Philip with his father as king to ensure a smooth succession.1

This practice of crowning an heir during the father's lifetime was a traditional strategy used by the Capetian dynasty to contribute to the stability and longevity of their rule. Following the ceremony, Philip’s uncles from the house of Champagne attempted to use the young king's position to exert control over France, a tutelage Philip eventually escaped by making his own political decisions before his father’s death in 1180. Philip II later became the first Capetian monarch not to have his own son crowned during his lifetime, reflecting the increased strength and security of the monarchy he had established.213