It gets even more complicated when these causes interact. A large part of the reason for the decline of smallholders and the rise of vast manors using serfs (slavery was in decline during that period), was the fact that farmers had to turn to the lords for protection from barbarians and roving bandits. The reason there were a lot of marauding bandits is that the armies were to busy fighting over who the next emperor was going to be to do their job of protecting the populace.
It gets even more complicated when these causes interact. A large part of the reason for the decline of smallholders and the rise of vast manors using serfs (slavery was in decline during that period), was the fact that farmers had to turn to the lords for protection from barbarians and roving bandits. The reason there were a lot of marauding bandits is that the armies were to busy fighting over who the next emperor was going to be to do their job of protecting the populace.