In the movie War for the Planet of the Apes:
The Humans feared an evolved emancipated Ape kind would replace their kind.
The humans waged war on apes fearing they may enslave them.
The Humans used apes to fight apes.
The humans eliminated any human infected by the virus that made apes smarter.
As apes got smarter the Humans became weaker.
The humans emprisoned apes and used them as a disposable workforce.
The Humans used few selected apes as prison guards.
Of course, it’s only a fiction!