Which was a cause for the disintegration of Charlemagne's empire after his death?

One major cause for the disintegration of Charlemagne's empire after his death in 814 was the lack of a strong central authority to maintain unity among the diverse regions. His grandsons, who inherited the empire, struggled with internal conflicts and succession disputes, leading to fragmentation. Additionally, external pressures from invading forces, such as the Vikings and Magyars, further weakened the empire and contributed to its eventual division.