"The failures of governmental prophecies in so many different contexts cannot be blamed on stupidity. "
No, but it can be blamed on arrogance and deliberate ignorance of human nature - a refusal to acknowledge their own limitations and to recognize that human motives are immutable.
Free market capitalism works because when taken as a whole, human beings function in ways that reflect their own best interests. Government attempts to control market forces are like attempts to control the weather. Arrogant, ignorant and powerless in the face of natural forces.
The best that can be done is to establish the boundaries to prevent encroachment onto the liberty of others to decide and act for themselves and then get out of the way.