I think this is the first article I’ve ever seen on the crisis of late antiquity and the transition to the Middle Ages that ignores the barbarian invasions and the collapse of the western Roman Empire, which occurred in the century preceding the volcanic cloud.
The Roman Empire was mostly broken into three (or more) independent states during the 3rd century, each ruled by its own emperor. The chunk of the empire ruled from Rome spent half of that century changing the supreme leader every couple of years on average. The British school about this attributes the political turmoil to "debased" currency, which is ridiculous. Economic activity actually took off during that time, with a rise in what we would call the middle class, prefiguring the late-medieval and post-medieval developments in Europe. Trade by sea (Indian Ocean) with India (which had been continuous throughout Hellenistic times, at least) and (via intermediaries) with China continued into the early 6th c. Trade across the intra-roman borders boomed while tax receipts fell. It's probably most accurate to call the crisis political, as the economic casualties appear to have been the rulers. Ingress from non-Roman barbarian areas was serious, and finally effectively addressed by Aurelian, who also knocked off his rival emperors and reunited the Empire.