The sheer amount of provinces on the continent makes the earliest bookmark unbalanced and rather ahistorical. I doubt the early Frankish kingdoms were individually stronger than the Islamic powers of the time, but because of how many provinces are under their control, their income and levies tend to skyrocket. It makes sense for 1066+ but that's about it. And yes, I understand the muslims receive a levy boost from their religion, as well as some Middle Eastern Christian denominations, but it's not quite enough. Starting in the Age of Vikings bookmark and upgrading your provinces a bit as one of the Frankish kingdoms makes your numbers go through the roof. At one point I was fielding 100k troops as a united Frankish Empire. Tell me that makes sense.