Why do you get deceived or brainwashed? It's not just because of insufficient information, but because when processing information, the brain activates certain more effortless yet more error-prone mechanisms under different conditions.

First, people mistake "repetition" for "truth"
The more often a statement is repeated, the easier the brain is to develop a sense of familiarity, and this sense of familiarity is intuitively perceived as a signal of credibility, thereby reducing further verification of authenticity.
Second, when lacking a stable cognitive framework to interpret a complex world
People tend to substitute simplicity for complexity, using "many people say so" or "it looks consistent" to replace analysis of evidence structure, essentially using the sense of quantity to substitute for causal judgment.
Third, under conditions of information overload or cognitive fatigue
The brain reduces deep thinking and instead relies on intuition, emotions, and group signals to make quick decisions. At this point, it is easier to accept simple, certain narratives that can explain everything because they reduce the psychological pressure caused by uncertainty.
Therefore, being misled is not always due to a lack of rationality, but because under certain conditions, the brain chooses a more effortless yet more error-prone way to understand the world.