So there was more exposure to different races that what's conventionally thought by people in the time periods.
Like a across the Mediterranean from Greece and Italy is Africa.
Conquering Northern Africa have been a goal for centuries before that.
Also the middle East has also been a goal to capture.
So for millennia in Europe the idea of conquering the lands of darker skinned people has been a thing.
And the 'black magic' traditions of the middle ages almost certainly drew their inspiration from the rituals of the Hellenistic mystery cults and related groups rather than any African tradition or cultures.
All the being said, I'm straying quite far out of my area of expertise here, so I'm certainly open to be proven wrong.