Answer:
Justinian's plague was caused by rat bites and it is said that 5,000 people died a day. It killed about half of the people under his rule, it made it easier for armies to defeat his empire.
The Barbarian attacks were increased because many people died from the plague and the Barbarians attacked from many different areas.
The Crusades were Christian warriors who tried to fight the Turks and Jews. The Byzantines were a part of the crusades that lost to the Muslims.
Different families fought for power and so many disagreements lead to a downfall in the government.
Step-by-step explanation: