Answer:
Milton Friedman was an American economist, founder of the theory of Monetarism. This theory establishes that the increase in the money supply (issuance of currency, mainly) generates inflation and unemployment, because the money supply must be governed by the number of transactions carried out in the market, and increase or decrease if these transactions do as well.
Therefore, Friedman was always critical of the expansionary policies of the different governments, mainly the Democrats. Thus, he considered that expansionary policies increased scarcity, while increasing the money supply and generating unemployment and inflation. For this reason, he uses this analogy of the Sahara to show his displeasure with the government, blaming it for the nation's economic problems.