Feudalism develops when there is not enough cash to go around.
IOTL, feudality develloped from the decline of post-imperial Roman administration, and the growing social mix of civil and military elites : it's not that bureaucrats disappeared, but that they get fused with nobles and landowners.
Mmoney was replaced and land as terms of exchange of services as soon as the VIth century, much earlier than the development of carolingian feudality, but what it did was bolster the rise of landed
potentes first in periphery, then in centers, pointing it's not a political decision, but rather a social development that Romano-Barbarian polities had to accomodate with : heck by the early VIIIth most of
militia took its power from their actual power rather than royal delegation, even if Carolingians tried to jury-rig the situation by replacing the royal power as provider of
potentia as well as
honors,
judicies and
beneficii (which admittedly was kept by Merovingians and the people they delegated these).
Which had for result to mix up potentia with not only administrative, but nobiliar duties : there is the origin of feudality, as it made the whole Frankish aristocracy entering a system on which they were still largely apart.
So, it's partially related to the fall of Roman state, and unusability of money as a way of exchange, but it's only one of the factors. It never prevented Frankish administration
militia and palatial
honestiores to gather much more imperial agents than Constantine had.
Not before benefices and honores becames so mixed than they're unseparatable can we speak of feudality.
Heck, when XIIth century made monetarization a thing again, it hardly weakened feudal entities : it just made the most powerful of them dominating.
Since North Africa is well placed for the trans-saharan gold trade
Tunisia isn't much that well placed tough : most of the roads that ended there either came from western or eastern Africa. Maybe more than for other North African regions, Africa was in a middle-man position (even if a very good strategical position to do so), while most of Africa's production was made on a domanial (or plantation) model. You had to wait Arab conquest and apparition of camels as a widespread transportation device (even if it was certainly known earlier).
Before the VIIth century, Africa was certainly more Mediterranean-minded than continental : not only due to geographical matters, but technical as well as economical (trade between western Africa and Mediterranean basin was mostly superficial).[/QUOTE]