The Vandals ruled successfully for 100 years, in which period renovation and economic growth took place, the archaeological evidence bares this out, though the written evidence is contrary. There may be something of a conflict of interest in relying on ecclesiastical and Roman accounts with an uncritical eye as regards the Vandal occupation of AP, especially given that still then a great mass of Donatists which inhabited the region were already being actively suppressed by the very same, and found kinship in the anti Niceanism of one another. Funny also you should mention Hippo, where Donatism still flourished to a good extent. The Roman governors and administration in AP were corrupt, Bonifatius and others were disliked by the inhabitants, their ability to govern and protect the region was minimal and they were constantly getting by on the skin of their teeth. One may forget that not the whole mass of inhabitants of AP were Nicene Christians. For your perusal, I have another document I'd like to share but I'll have to wait until I'm on desktop and then we can take it further from there. You may have to wait until tomorrow for me to actually sit down, find them, translate etc, but remind me and I will get around to it.

https://www.academia.edu/27135277/The_Vandal_impact_on_North_Africa