Romano Britons, Is Stilico a Soldier in Britannia?

A massive horde of swoebi, allons, and vandals defeated the Frankish forces that were stationed there. And as a result, the barbarians were getting confident again. So why would the British soldiers try to rebel and establish a new emperor? The soldiers actually had a legitimate beef with the central government. Their military strength was being sacrificed for a city they had no real ties to.