What happened to Charlemagne's empire after he died and why?

After Charlemagne's death in 814, his empire began to fragment due to internal divisions and external pressures. His grandson, Louis the Pious, struggled to maintain control over the vast territories, leading to conflicts among his sons. The empire ultimately split in 843 with the Treaty of Verdun, which divided it into three kingdoms, marking the beginning of the decline of centralized Carolingian power and the rise of regional identities in Europe.