Does anyone wonder why the nobles built castles? hummmm? TO PROTECT THEM FROM THE PEASANTS THEY WERE COLLECTING TAX FROM (in the form of food and product of their work). It was the INTRODUCTION OF FEUDALISM that caused all this tax stuff. Everyone just lived on the land before that.
The peasants would regularly just burn down the nobleman's house.
The reason why the nobles were able to build those castles was with the approval of the King. The King needed his nobles to collect the tributes aka TAXES. The nobles got to live very removed from real life in the castle on standby until the King called upon them to go to war for him. That was the price of their nobility. AND OFTEN the King answered to the Pope.