Of course, you discount the lack of enthusiasm on the part of the monophysites for defending the territory of the 'melkite' Emperor.
Now which 70 years was that? Certainly not during the reign of Justinian or his immediate successors during which notable iconography graced newly completed churches in Ravenna. Ones just before the iconoclasts took up the wholesale destruction of religious art?
And I guess George of Pisidia, the best secular poet of the Christian Imperial period doesn't count for anything, nor the composition of some of the most moving devotional poetry ever written (to my mind in any religious tradition)--the Great Canon of St. Andrew of Crete.
And wouldn't you know, the silk trade between the Empire and China died out just when some Christian monks manged to smuggle silkworm eggs back to Constantinople, c. 553, beginning an industry which lasted until the Empire fell.
Then there are the Iconoclasts. There was some stir in the 4th century, but there was a significant pause until the 8th century, and then only in the Eastern church. The Dark Ages began on or about 538 AD (and there's a fellow who has scientific evidence regarding the specific date the catastrophe that precipitated it happened). Anyway, 538 is in the 6th century.
BTW, BEFORE the Dark Ages began there really were more places of interest in the Roman world than AFTER. Things did not really revolve around Byzantium and its environs.
Things were different during this period.
"A team of geologists believes it has found the incoming space rock's impact crater, and dating suggests its formation coincided with the celestial vision said to have converted a future Roman emperor to Christianity. "