The empire was already on the edge of the collapse, there were several reasons of the fall: political crisis, economic weakness, military problems, rise of Christianity, invasion of Germanic tribes. It represents the end of the ancient times and the beginning of the middle ages. The Roman empire were a huge unified territory. With the end of it, the barbarian tribes took over the territories, making their own kingdoms (Kingdom of Vandals/Ostrogoths/Gepids). Christian church got more power.