Yeah, there are many of us here. This is the start of people getting more power.
Wait, so if i'm free, I can't be arrested without a reason?
Nope, if people followed the Magna Carta then no one, not even the king, could arrest you without reason.
After the Black Plague, peasants and serfs abandoned their manors to get paying jobs in towns and cities. They were able to do this because of the lack of people that were able to work. This weakened feudalism.
I'll sign it, but I don't want to.
The towns attracted serfs and peasants because it allowed them to escape from their rotten position that they had back on their manor. This weakened feudalism because without serfs and peasants, the whole thing falls apart.
100 year war
The feudal lord are dying! Hurrah!
The Magna Carta was the first document that theorizes the idea of no man being above the law, not even the king. This protected the people and was the birth of democracy.
Decline of feudalism
King John very reluctantly signed the document that guaranteed his citizens rights, like right to a free trial.
Many of the feudal lords died in the 100 years war. This played a part in the decline of feudalism because the without the feudal lords, the feudal system is no more.