What was a major cause of the civil wars that ended the roman empire

the noble might have thought that the system was far because they had lot of things and riches and the serf would have thought that the feudal system was un fair because of the way they were treated.

according to my research (britannica and quizlet) the first settlements were along the huang river because it could give the crops more fertile soil that really it out. this was due to the yellow slit caused by floods of the river.