Little confused by the preview

It's supposed to be hypothetical - they're doing the "experiment" in class - however, the movie shows actual apocalyptic events to make it interesting.

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"Could you please get your head out of your ass? It's not a hat!" - Pitch Perfect

It's all imaginary, they're sitting in the class, and it's much less interesting than they make it out to be.

The increase in human knowledge is the cause of the decline of religions.

actually it is kinda neither. it is supposed to be hypthetical, but if you think about it, it kinda does not work either way.

"laugh and the world laughs with you. Weep and you weep alone." - Dae-su Oh