Though lions are carnivores, humans are rarely on their menu. We are not part of their regular diet.
In Africa, in terms of attacks on humans, the big cats aren't what you should worry about. There's a much bigger risk of getting attacked by a hippo or a cape buffalo, for example.
And the most lethal animal on the African continent is probably the mosquito.
Even with all of this, introducing lions to the Great Plains is probably not a good idea.
Well, yes, but that's because the Africans are not so stupid as to allow them to roam freely anywhere near them.
I doubt that the predators don't know this as well, and stay pretty far away.
They don't call them "rouges" for nothing.
These people are bone crushingly stupid.