The Irish resisted conquest longer than any of the Celtic peoples of the British Isles. Unlike most of Britain the Irish were never conquered by the Romans, the Anglo/Saxons, or the Danes. Even at the height of Viking power, the Norse held only areas of costal Ireland, while the interior remained in the hands of the Irish.
As for your Carolingian Franks, after Charlemane croaked, it was all downhill. In 911 the Carolingians lost control of their territory in what is now modern day Germany. In 987 they lost what is modern day France.
Also, while the Huns and Germanic tribes, including the early Franks, were rampaging across Europe destroying civilization and driving Europe into the Dark Ages, the Irish played a critical role in preserving and eventually refounding Western European civilization.
LINKY
BBC Documentary
And... The existence and deeds of Irish/Celtic heroes of legend are as real as many if not most of the characters and deeds of persons in the Torah, the Bible, or the Quran.
Oh, and one more thing. GO SEAHAWKS!