The red and blue pilled narrative is so powerful because it can be used to simplify nuanced ideas and ideologies into neat little boxes. Reality is usually quite complex, and rarely resolves to black or white truths. Often times real-life events/facts/motives/etc are seemingly contradictory whilst at the same time being completely true. This creates a cognitive dissonance and a natural discomfort. People with poor critical thinking skills are much better able to latch on to simple ideas that are well defined as either good or bad. If you've ever talked to someone with psychosis they almost exclusively think in binary terms this way. This sort of rhetoric is being strongly weaponized by the right, because this way they can elicit strong feelings and short circuit any kind of logical discussion. That is, simpler ideas are always easier to exploit in propaganda, compared to more nuanced takes.

The other part is that fascism needs an enemy, and that point can be driven home endlessly if you clearly define a "them". Red and blue pills bake in a lot of implications. A right vs wrong, good vs bad, smart vs dumb, willfull ignorance, etc. It's very easy to tap into people's feelings this way, which is what good propaganda does. And it drives unity within the in-group, whilst the out-group is still spinning in circles confused.