The time after the fall of the Roman Empire was a period of civilizational change. The Roman Empire had been one of the great civilizations. It covered a massive portion of the known world. Towards it’s decline, it split into the Western and the Eastern halves. The Eastern half continued as the Greek-influenced Byzantine Empire for a thousand more years before being overrun by the Ottomans (who, in some ways, saw themselves as the successors of Rome).
In the West, the fall of the empire occurred through a gradual but eventually dramatic takeover by the Goths and other tribes. These tribes took over the former empire via immigration and a series of invasions. The fall brought about a period of questioning and relative lack of vibrancy. It was with the Renaissance that they rediscovered its bearings. The West began to bloom again. With the onset of the scientific and industrial revolutions, the West regained its civilization in a way.