Foreshadowing

In a scripted video it does two jobs at once. Narratively it makes the payoff feel earned instead of arbitrary. Structurally it opens a loop, and open loops are the main reason people stay past the point where they would otherwise leave. A line as small as saying this is the bit that goes wrong later can buy you several minutes. Both failure modes are common. One is planting and then failing to pay off, which viewers register as a broken promise. The other is planting so heavily that the payoff is obvious and there is nothing left to wait for. Plant it once and let it sit.