Probably because of the united hate of the Roman Empire. The empire kind of created two cultures. The on inside it's borders, and the one outside it's borders. Even the Romans themselves would note that the "barbarians" had a similar culture between themselves. Still there were many rivalries among the groups that destroyed the Western Roman Empire, and surprisingly, they used mixed Roman culture with there's.
The best answer would be They wanted to end the practice of slavery and free enslaved workers.
Answer: Primary Source
Explanation:
The veteran is an eye witness he was there and experienced it making his story a primary source.