Why did the visigoths rebel against Romans?

There was a first rebellion when the Visigoths were first allowed to settle in the lower Danube area of the Roman Empire. This was because there was a famine and the Visigoths did not receive any help. Then peace was made. Later, Alaric I, a Visigoth king, rebelled. The reasons for this are unclear. It has been speculated that Alaric wanted to become a general of the Roman army, but this was not granted.