No, look there Hugh Capet - Wikipedia
Hugue Capet is the King of the Franks, not of the French. Of course there is a link, but Franks are not exactly French. Franks are germanics people elite.
Charlemagne didnt stop the Moors in Poitier. It was Charles Martel and he did this with swordmens
France have a cavalry tradition, but England too.Thinking France is the top cavalry is a cliché. Also nowadays, germans have a strong cavalry history and the best skill in horses olympic game or domestication in history. You can see this on wikipedia,
They put a pv bonus for Abassid, but this faction is really not the best on the sea. Others faction have a strong bonus like the France who dominate the naval maps. I guess its only to equilibrate.
The Mongols, I personaly think they added them for four reasons :
First, because like the Vikings they are very popular in the common culture with Gengis Khan.They are very popular in occident as the Mongol Periple. Thousand of horsmens surgering from the far steppes to destroy every thing until the West.
Second, because they have a high customer potential. East Asia is nearly 4 billions people who can identificate themselve to this faction.
Third, because they are extremly important in the middle age history. They destroyed the Abassid reign and push until Ostria begining a serious threat for Europe. Every people in Europe know them as barbarics hordes.
Four, because their gameplay based on hit and run, raids, nomadism is very original and exciting.
If you compare with the christian spain before the reconquista, these four point are quite empty. They are unknown, spainish are fiew, the majority hispanic community is latino and they want meso america civ, then their gameplay wont be so original.