It is my understanding that Asian elephants are easier to tame by humans than African elephants, which is evident just by seeing how elephants are used in parts of Asia and how they are used (not) in Africa. Also circus elephants, when they were still common, would always be Asian elephants and not African ones. The reason I'm pointing this out is that I wonder whether the North African subspecies was more amenable to taming than still extant subspecies of the African elephant.
There are multiple species of African elephants, and the North African elephant may yet turn out to be related if not identical to one of the others: https://en.wikipedia.org/wiki/North_African_elephant#Taxonom... The African forest elephant is of similar size, and it would be interesting if the forest elephant is indeed more easily trained.