The human brain is more of a "rationalization engine" than anything else
Just no. Some people tend to rationalize everything, sometimes post-factum, that much is true, but the quoted statement is just wrong.
First and foremost, our brain is emotional and impulsive. Consciousness and rationalization comes after, as speech is a learned skill, and we use speech to rationalize in the first place.
False pretenses are a thing, but it exists to deceive a larger group of people for the benefit of a smaller one. And yes, it means that the deceiver can be the sole beneficiary, even if often than not it isn't the case.