but to answer the OP
Yes North Africa was pretty much a rich region in the early medieval period. If you play the early bookmarks 867 and 769, North Africa, especially Kingdom of Africa, should be among the richest regions of the Mediterrean. That is correct. At the same time the central and western parts of Maghreb were not that rich and developed, but the tribal structure of local populations joined with islamic teaching gave them military power which made them relatively stronger than their neighbours. The game unfortunately does not reflect this very well, but if these regions have strong military, it is correct.
We should also keep in mind one thing:
The same global environmental process which made Europe warmer in the 11th and 12th centuries, resulting in unprecedented demographic expansion (which later caused also economic and political expansion) is the same process which also made other regions of northern hemisphere warmer, such as the Sahel, North Africa, Middle East and the Asian Steppes.
While Europe had abundant sources of water, these other regions did not, and warmer climate there meand aridization. In the steppe and semi-desertish regions it caused either collapse or decline of agricultural empires (Ghana, Central Asian kingdoms such as Samanids), or migration of local nomads (Asian steppe, Sahara). For the richer regions directly neighbouring to those steppe or semi-desert areas it meant invasions of the steppe/semi-desert nomads. This is the start of Mongol migrations, Turks flooding Persia and the Middle East all the way to Anatolia, Hilalian Arabs flooding Ifriqiya, Saharan Berbers migrating either to the Sahel or Morocco.
We all know the consequences of this and we all tend to associate the results to the cultures and institutions of named regions. But the fact was that from the developed regions of the Western Old world, Western Europe was probably the only one which wasn't exposed to invasions (it had enough of them in previous centuries) and enjoyed both positives of this warmer period. North Africa OTOH suffered both negatives (aridization + being target of migration).
The fact that Western Europe had just developed some innovative technologies and institutions which allowed it to boost the development even more is something which gave it relative advantage to other regions. The biggest advantage, however, was that it was the only developed region safe from external invasions. OTOH, its demographic explosion caused expansion of its social, political and economic system... which lasted another few centuries (that is due to social, political and other conditions, but the initial kick was from mother nature and geigraphy).
In fact, wasn’t there a lot of continuity between Roman Africa Proconsularis and Islamic Ifriqiya in those initial centuries? Whether under Roman, Vandal, or Arab rule, the highly urbanized population of that region was pretty much still Latinized (or Islamized) Punic-Berber, right? The destruction of Carthage was undoubtedly very disruptive considering the scale of the city, but it also wasn’t the only urban center of the time.
Unless I’m wrong (and I could be, I’m far from an expert) the urban civilization didn’t disappear after the Roman and Byzantine governors left, and neither did the population. Ifriqiyans were known as an actual cultural group, aren’t they?
To be honest, I'm far from being expert on Late antiquity. I only have what one semester lecture and few additional books taught me.
But as far as I know the Islamic period of Maghreb, the original Romanized/Latinized population remained in place. Some of the city elites probably left, but that was joined by Arabic city elites, which caused that the urban population of Maghreb was Arabized quite briefly.
While the destruction of Cartaghe deffinitely was fatal for the city itself, we should keep in mind that at the same time the center of political and economic power moved to the newly founded capital Kairouan, which was by far the largest urban center of the region by the Hillalian invasion in 1050's.
You are of course right that Cartaghe was definitely not the only urban center of the area and even if not a single person moved to Kairouan (which is very improbable), the urban life did survive and as far as we know, did flourish also under Arab-muslim rule. I can't really compare it to the Roman pre-Vandal period, but it certainly was at least as developed as Pre-Islamic, or more.
So it’s not so much that the change in the flags flying over the city made any difference, the Romanized population was still there and they didn’t disappear after Islam took over any more than they disappeared when the Vandals briefly took over.
I can't say for sure, since I don't know the history of the area in Vandal period, but this is how I would describe it. It doesn't mean I'm right, though.
I had no idea about the Fatimids sending those populations over though. I’ve always wondered when urban culture disappeared in North Africa, and I guess this answers that.
I'm glad I could be helpful. As I said, the political aspect in this migration might be overrated ever since Ibn Khaldun, who wrote the history of Maghreb 3 centuries after these events (OTOH his standards as a historian were equaled by others (both in the
West and the
East) only in the late 19th century). There is only abundant evidence that these tribes were causing Fatimids a lot of problems, that the Fatimids had promised these tribes their previously owned lands and that it happened after the Zirids broke apart from their previous overlords. The migration might as well be caused also by other factors (considering the power of these tribes, it is doubtful that the Fatimids were powerfull enough to force them to move).
Do you think the game accurately reflects this change from the early bookmarks to 1066?
I am partialy responsible fot the current setup, so it is hard to say objective answer. I would say that it does its best possible with existing mechanics. Or almost the best...
The game still fails to represent the tribal structure of North African Berbers as well as the Arabic and other semi-desert tribes and societies. The tribal government in early bookmarks in Morocco does not reflect the Berber tribes and the Iqta government does not reflect the tribal society of Hilalian nomadic tribes, but...
If I ever find some time for modding again, I would love to do a mod to improve it. Or dream that a DLC or at least a patch with improvement of Arab tribes will come.