The Bubonic Plague was a dangerous disease that killed millions through China to Europe. As a result of this, the peasants gained much power.
The Medeviel people did take shipments and trades from Asia, however, they did not know that many were dying there.
The Bubonic plague possibly came from China to Europe on a boat from China to Italy.
WE DEMAND MORE POWER!!
Fleas and Rats such as this one started the plague. The disease usally came from animals, however, humans obviously could get it too.
As the Bubonic Plague had many causes of it spreading so quickly, Another cause of it would be them not having any hygiene, such as baths or even washing their hands. In addition, doctors in this time believed if they took out the bad blood that they would be cured, the loss of blood made it even more dangerous and let it spread to them even more.
As result of all of this, the peasents gained much more power because they knew the Nobles would have to employ them because many peple had died, letting them have more power and rights. Which weakened the Feudalism scale.