One easy to understand reason is that central planners in the days of the Soviet Union had to set over 24 million prices. Nobody is capable of setting and changing 24 million prices in a way that will direct resources and output in an efficient manner.

For that, each of the 24 million prices would have to be weighed and set against each of the other 24 million prices. in order to provide incentives for resources to go where they were most in demand by producers and output to go where it was most in demand by consumers.

In a market economy, however, nobody has to take on such an impossible task. Each producer and each consumer need only be concerned with the relatively few prices relevant to their own decisions, with coordination of the economy being left to supply and demand.

In short, amateurs were able to outperform professionals in the economy because the amateurs did not take on tasks beyond the capability of any human being or any manageable group of human beings.

Put differently, "expertise" includes only a small band of knowledge out of the vast spectrum of knowledge required for dealing with many real world complications.

Nothing is easier than for experts with that small band of knowledge to imagine that they are so much wiser than others. Central planning is only the most demonstrable failure of such thinking. The disasters from other kinds of social engineering involve much the same problem.

Surgeons succeed because they stick to surgery. But if we were to put surgeons in control of commodity speculation, criminal justice and rocket science, they would probably fail as disastrously as central planners.