There were many causes of the collapse of the Roman empire. One theory is that the empire just got too big to control politically and to keep a good economy going. There was a lack of circulatory currency in the western portion of the empire because of the widespread looting of the Roman treasury by barbarian invaders. This resulted in a trade deficit with the eastern regions of the empire. Another economic factor in the fall of Rome was that the climate and rainfall patterns were changing and becoming more unstable. The weather began to alternate between hot droughts and cold rainy seasons. The result was decreasing crop yields, and some historians say that the Romans began conducting large irrigation projects. These projects required water to be stored in large reservoirs where the water became stagnant and attracted mosquitoes. These were carriers of malaria, which and killed much of the population.
Another reason why Rome collapsed was that the military became weak and allowed barbarians to invade the Empire at different times. A reason why the military became so weak after having such a great reputation is that new recruits had no incentive to join the army. In the past, citizenship was granted to soldiers after they had served. Citizenship was a great right since it gave way to possible political power. However, in the later empire, citizenship was granted to all males and citizenship was no longer a reason to join the military. Also, the loyalty of the soldiers that did join was divided among many powerful sources.
The morale of the people declined and the empire became less "Romanized". The Germanic neighbors of the Roman empire assimilated themselves into the empire. Also, since the rule of the emperor Constantine, Christianity was now the official religion of the empire. The church began to establish its own structure and hierarchy, which interfered with the way that the ruling powers always operated in the Roman empire. The introduction of Islam into some parts of the empire also divided the empire.