It’s been a minute since I saw it, but the root reason was that they were taking these young bodies to more or less extend their lives, maybe indefinitely. They kidnap black people because their missing reports are given a lower priority than whites, which is shown in the scene when Andre’s TSA friend (Rod?) goes to the police and they dismiss him about finding the missing black man from the beginning of the movie. Granted, his story and theory about the abduction is hard to believe, but there should’ve been some response to the guy being seen more than “he looks found to me”

And don’t get it twisted, the white people are racist, but they weren’t skinheaded, card-carrying, hood-wearing, hard-r racists. They were a modern affluent family you could find in many suburbs. Neoliberal type racism

And the behavior of the people who were already taken over? They wouldn’t be acting like servants normally. That’s why they seemed so strange, because they were putting on an act to get Chris taken over, and the only way they knew how to act out a black person was as a servant.