Why did many nobles see their power increase in the 800s?

In the 800s, many nobles saw their power increase due to the fragmentation of centralized authority, particularly following the decline of the Carolingian Empire. As local rulers, they capitalized on the weakening of royal power, establishing their own domains and asserting greater control over land and resources. Additionally, the need for local governance and military protection amidst Viking, Magyar, and Saracen invasions allowed nobles to solidify their influence and become key figures in their regions. This shift marked a transition towards feudalism, where loyalty and service were exchanged for protection and land.