Answer:
The plague or Black Death brought about a significant decline in feudalism. In 1348 The Black Death swept through the majority of Europe killing people in the millions. This massive tragedy resulted in the decline of Europe's labor and surf forces and in consequence, the income and wages for the peasant class increased substantially. The higher class naturally did not accept this which in return angered the lower class; thus, resulting in turmoil between both classes. The peasant class soon overcame the higher class effectively abolishing serfdom and feudalism in Europe as a whole.
The shifting of powers from lords to common people saw the decline of feudalism as well. The Hundred Years war brought about new ideas and inventions most notably the inventions of firearms, cannos, and gunpowder. These innovations in military technology made knights and castles seem less reliable. The war promoted feelings of pride and nationalism, the system shifted towards the people and loyalty to monarchs rather than to nobility.
In essence Feudal society as a whole fell due to advancements in technology and agriculture; and the effects of the bubonic plague.
