Oh p.s. the reason that Charlemagne is interesting is more due to The Saxons, then how that went to "Anglo-Saxons", where people were from, were they went, how those people became "us".....many within USA. European History is fascinating as that relates to who people are, their lineage and what people's ancestors lived in.
And it also illuminates what Islam is and shines light on how unfortunate it is that, as you said, Modern day Europe will wind up losing after all, to Islam. That so many fought to repel.
Just to clarify what was meant by Charlemagne (Charles The Great) being "interesting". Not so much his epic battles and defeats of Muslims (and those of his Dad and Grandfather, in what wqas called "Francia" at that point) cuz Islam is boring all it ever does is Kill thats all Islam has ever done.
The stuff that the ancestors of Anglo-Saxons (and other tribes withiin what now is Germany, France, Denmark etc) went thru is fascinating though....what these people did, where they went and how that led us to now.