Final answer:
The migration of peasants to towns weakened the manor system due to the population decline caused by the Black Death, the labor shortage it created in the countryside, and the higher demand for labor in cities. This allowed peasants to negotiate for better conditions and weakened the power of landlords.
Step-by-step explanation:
The migration of peasants to towns weakened the manor system for several reasons. Firstly, the Black Death pandemic in the 14th century resulted in a significant decrease in the population. This led to a labor shortage in the countryside, causing landlords to offer better terms of labor and wages to attract workers in order to replace the dead. Secondly, the high demand for labor in the cities created opportunities for peasants to seek wage labor and employment in urban areas, further depleting the labor force in the countryside. Lastly, with fewer peasants available to work on manorial estates, those who remained in the rural areas were able to negotiate for better wages and rights, weakening the hold that landlords had over them.