This process is flexible and it encourages creativity. It also denies to anyone the power to unilaterally impose his own vision on others.A commenter states:
In brief, to advise "Let the market handle it" is a shorthand way of saying, "I have no simplistic plan for dealing with this problem; indeed, I reject all simplistic plans. Only a competitive, decentralized institution interlaced with dependable feedback loops -- the market -- can be relied upon to discover and implement a sufficiently detailed way to handle the problem in question."
Selfish can justifiably be described as self-interested. This leaves us with an order in which people need to make an effort at providing goods and services which other people need and desire, a very social order. Alternatively, central authorities or elites can decide many things. This is less social and in an extreme enough form, downright anti-social.
It is easy to comprehend the selfish motive of a rotten king, but much more difficult to perceive the complex of selfish motivations in the hypothetical "collective".
So they have rejected the idea of being subjected to the selfish rule of kings, but not the idea of being ruled. Or rather, they believe that others must be ruled to restrain their selfish impulses.
What is the market?
It is the venue where people satisfy their selfish needs and desires by satisfying the selfish needs and desires of others through trade.