Also, the plague of Justinian (541–549 AD) was the first major outbreak of the first plague pandemic (the Black Death, caused by the bacterium Yersinia pestis), collapsed the economies of the neighboring Sasanian (Persian) Empire and the Byzantine (Eastern Roman) Empire and especially its capital, Constantinople.
As well as the power vacuum in the neighboring areas, Arabia experienced a gold rush around that time, that empowered their elite to rise to prominence within the weakened former Persian Empire.
It occurred to me to check out Cassiodorus and his reports of strange weather and pale sun and moon in 536. Found a detailed Wikipedia report. Apparently there were 3 major volcanoes starting 535-536 and then followed at 3 or 4 years apart by 2 more. These could easily explain a number of world history disasters and upheavals like Justinian’s Plague, and the rise of Islam, and major droughts. This link lists a number of such occurences and References and possible volcanoes, as well as possibly some meteoric events.
https://en.wikipedia.org/wiki/Volcanic_winter_of_536