I don’t disagree about the distorting effects of power and money interests. What happens though in the mind of a cigarette company executive or institutionalized scientists promoting a wrong and harmful idea? Rational, objective assessment of the facts is overwhelmed by the power of self interest. Cognitive dissonance shifts the person’s beliefs to support their behavior, so they actually believe themselves. This is a fundamentally irrational dynamic, an override of what would be the person’s usual capacity for rational assessment of the facts. They are literally blinded by self interest. That is different from merely having an incorrect but rationally based belief, like that one should lower one’s cholesterol intake. So one may act rationally on an incorrect understanding (cholesterol is bad) but the incorrect understanding may be formed or maintained rationally or for non-rational reasons such as self interest, groupthink, or due to prejudice or other cognitive errors and distortions. Humans are of course capable of rationality. It’s just that our rationality is heavily circumscribed by non rational factors.