Can you elaborate a little more on why you would argue it had a positive effect? I, personally, would argue that the Fall of the West had a mostly negative impact on the ERE, primarily for geo-political and strategic reasons, but I'd like a bit more context so that I can focus the answer for you.

Presumably the effects were negative. Not only did the east spend resources trying to reconquer or reestablish the empire in the west but the sense of decline had set in with the fall of Rome and the east increasingly thought of itself as a singular empire and not just the eastern half like before.