Answer:
Bad leadership and outside invasions.
Step-by-step explanation:
The emperor of Rome had massive feasts while extravagantly spending money. Then, he bribed soldiers with money to stay loyal. Therefore, there wasn't a lot of money in the treasury. So, the emperor decided to mint lots of money, making the value of the coins decrease.
Also, outside civilizations attacked Rome using the roads emperors created. Yes, those roads were good for trade. However, they all lead to Rome as well. Therefore, the outsiders found the roads, which led them to Rome.