Remember I mentioned Isaac Arhrur's youtube channel? No, I'm not paid for advertisement :-) But I've just watched another episode, namely "Welcome to the Galactic Community!" and it said how a space faring civilization would have more anthropologists that we have people, so if they have been studying us before making contact, they would know us better then we know ourselves, including out psychology, and using that they would be able to talk us into being their food in a way we would be overjoyed for such a great opportunity.

Actually, the idea of humans not simply eating each other, but being a willing slave/food race for a more advanced space civilization was in my mind for some time, although I never bothered to think deeper into it (though now I think of it I do have one never finished story where it's humans who come to an alien race and and offer in exchange for military protection half of human population as slaves, who are happy to be slaves because humans characteristic in that world is empathy… though the whole thing is actually a movie filmed inside a computer simulation, so while they do die inside that simulation, they don't die for real… maybe I should return and finish it some day…)

Anyway, where was I?.. Ah, basically, what I wanted to say is that now it doesn't have to be just "let's imagine a universe where just out of nowhere humans are happy to be slaves and food", instead there can be a valid reasoning for that. And it doesn't even have to be anything one could call brainwashing or deception, but just being good enough at convincing that people would be genuinely happy to become slaves/food/whatever.