The market decides how much to produce, capitalism scales up the best producers.
Producers want monopolies but somehow we need to keep a flow of promising new producers launching so that doesn't happen, because it screws up the market (the monopolist produces less and takes more for it).
The actual word 'competition' did not mean winner takes it all in the Ancient Greek flavour of the word, it has also been newspeaked by Capitalism. Originally there was some honour to competition. See also where the word 'agony' comes from:
Producers want monopolies but somehow we need to keep a flow of promising new producers launching so that doesn't happen, because it screws up the market (the monopolist produces less and takes more for it).