The Plague of Justinian was named after Justinian I, Emperor of the Byzantine Empire at the time of the first outbreak in 541 AD. The plague was named after him because a huge proportion of those killed were in the Byzantine Empire. Procopius of Caesarea blamed Justinian himself (who got the plague, but survived) for the outbreak. He believed that the plague was a punishment from God, and that Justinian was some kind of devil. This perception could have had profoundly negative effects on Justinian's future efforts to reunite the Western and Eastern Roman Empires, eventually leading to the end of the Roman Empire as a whole. Additionally, the Byzantine Empire itself was incredibly weakened by the plague, in terms of population, defense, economy and agriculture. The Byzantine Empire gradually lost territory after the plague. This also would have greatly undermined Justinian's attempts at re-unifying the Empire.
[P1] Justinian I was blamed for the Plague of Justinian. [P2] This undermined future efforts to reunite the Roman Empire which could have prevented its eventual fall.