The factor that most contributed to the development of the manor system in Western Europe after the fall of the Roman Empire is lack of a central authority and infrastructure.
With the collapse of the Roman Empire, there was a power vacuum and a decline in centralized governance, leading to the need for localized systems of management and protection. The manor system emerged as a response to these conditions, providing a structured community where lords and peasants could work together for mutual benefit, often with the lord offering protection and the peasants providing labor in exchange.