Question: What was an economic effect of the war during which Hayek started working on Abuse of Reason?

Knowledge 1: Friedrich Hayek
During World War II, Hayek began the ‘Abuse of Reason’ project. His goal was to show how a number of then-popular doctrines and beliefs had a common origin in some fundamental misconceptions about the social science. In his philosophy of science, which has much in common with that of his good friend Karl Popper, Hayek was highly critical of what he termed scientism: a false understanding of the methods of science that has been mistakenly forced upon the social sciences, but that is contrary to the practices of genuine science. Usually, scientism involves combining the philosophers' ancient demand for demonstrative justification with the associationists' false view that all scientific explanations are simple two-variable linear relationships. [SEP] Knowledge 2: Aftermath of World War II
At the end of the war, millions of people were dead and millions homeless, the European economy had collapsed, and much of the European industrial infrastructure had been destroyed. The Soviet Union, too, had been heavily affected. In response, in 1947, U.S. Secretary of State George Marshall devised the ``European Recovery Program '', which became known as the Marshall Plan. Under the plan, during 1948 -- 1952 the United States government allocated US $13 billion (US $139 billion in 2016 dollars) for the reconstruction of Western Europe.
Knowledge 1: Friedrich Hayek
During World War II, Hayek began the ‘Abuse of Reason’ project. His goal was to show how a number of then-popular doctrines and beliefs had a common origin in some fundamental misconceptions about the social science. In his philosophy of science, which has much in common with that of his good friend Karl Popper, Hayek was highly critical of what he termed scientism: a false understanding of the methods of science that has been mistakenly forced upon the social sciences, but that is contrary to the practices of genuine science. Usually, scientism involves combining the philosophers' ancient demand for demonstrative justification with the associationists' false view that all scientific explanations are simple two-variable linear relationships. [SEP] Knowledge 2: Karl Popper
While there is some dispute as to the matter of influence, Popper had a long-standing and close friendship with economist Friedrich Hayek, who was also brought to the London School of Economics from Vienna. Each found support and similarities in the other's work, citing each other often, though not without qualification. In a letter to Hayek in 1944, Popper stated, "I think I have learnt more from you than from any other living thinker, except perhaps Alfred Tarski." Popper dedicated his Conjectures and Refutations to Hayek. For his part, Hayek dedicated a collection of papers, Studies in Philosophy, Politics, and Economics, to Popper, and in 1982 said, "...ever since his Logik der Forschung first came out in 1934, I have been a complete adherent to his general theory of methodology."
Knowledge 1: Friedrich Hayek
During World War II, Hayek began the ‘Abuse of Reason’ project. His goal was to show how a number of then-popular doctrines and beliefs had a common origin in some fundamental misconceptions about the social science. In his philosophy of science, which has much in common with that of his good friend Karl Popper, Hayek was highly critical of what he termed scientism: a false understanding of the methods of science that has been mistakenly forced upon the social sciences, but that is contrary to the practices of genuine science. Usually, scientism involves combining the philosophers' ancient demand for demonstrative justification with the associationists' false view that all scientific explanations are simple two-variable linear relationships. [SEP] Knowledge 2: Friedrich Hayek
Arthur M. Diamond argues Hayek's problems arise when he goes beyond claims that can be evaluated within economic science. Diamond argued that: “The human mind, Hayek says, is not just limited in its ability to synthesize a vast array of concrete facts, it is also limited in its ability to give a deductively sound ground to ethics. Here is where the tension develops, for he also wants to give a reasoned moral defense of the free market. He is an intellectual skeptic who wants to give political philosophy a secure intellectual foundation. It is thus not too surprising that what results is confused and contradictory.”

Answer: much of the European industrial infrastructure had been destroyed