I think you can certainly google most of it. But certainly the combination of climatic change and the bubonic plague certainly helped bring down the plans of th

I think you can certainly google most of it. But certainly the combination of climatic change and the bubonic plague certainly helped bring down the plans of the Emperor Justinian to reunite the Empire. An excellent resource is the Fall of Rome Podcast. Most historians will agree that no one reason alone caused the Empire to fall, rather it's a combination of factors that together brought it down.