Explanation: While barbarian invasions definitely contributed a great deal to the destruction of the Roman Empire... most of the barbarian tribes which invaded had no intention of destroying the Roman Empire. Many, in fact, admired it (or at least its magnificent standard of wealth and power), and only desired to escape other mass migrations, or climate change as the northern regions of Europe became colder and even more inhospitable. To that end, their general demand was not "GIVE US THE EMPIRE, YOU SOFT 'CIVILIZED' CREATURES. LET US FEAST ON ITS FLESH", but "Please let us settle safely and securely in your lands, we will literally die out here if we don't."

The Roman Empire at this time was... not always accommodating, for a wide variety of reasons, not all of said reasons good, moral, or even sound on the basis of selfishness and self-interest. Leading to said tribes forcing their way, and settlement.

The Huns, on the other hand, were very recent arrivals to Europe. Some suspect that they were related to the nomadic peoples who tormented China not long before; others suggest a more 'generic' Central Asian origin. In either case, the main interest of the Huns was "Loot, pasturage, domination", possibly in that order. They had come a great distance and had no cultural conception of Roman 'greatness'; they wanted a new land to call their own, and if the local sedentary grass-eaters couldn't defend the territory or their goods, so much the easier became their goal!

Ricimer was a Germanic warlord in the employ of the Western Roman Empire who took the cruelest paths to power he could find, but was intelligent and cunning enough to escape consequences all the while. Most notably, he helped his lifelong friend, the Emperor Majorian, universally recognized as a good leader, to power. Then betrayed him, undermined his rule, couped him, and tortured him to death. He probably would've enjoyed carving Locksley's heart out with a spoon ("Because it's dull. It will hurt more, you twit!")