Answer:
Emergency times call for Emergency measures.
The United States was at war and so needed as many resources as it could gather to defend itself against the aggression of the Central powers. In times like such where the security of the nation is threatened, emergency measures by the government are necessary to ensure victory and so this was justified.
Resource allocation.
In war, there are many things that the government needs to spend money on ranging from weapons acquisition to the salaries of the millions that were called up to fight. Money needs to be allocated carefully to each of these so that the war effort is sustained.
If the War Industries Board had not taken over and people charged the government whatever they wanted, the government would be forced to pay high prices for certain goods and this would reduce the amount of money left for other key aspects of the war effort.
Efficiency and Coordination
In matters of war, it is important that the efforts of a country are coordinated so that there will be efficiency in it's war response. This was why the War Industries Board was important. By taking over and setting prices, the Board was able to produce what needed to be produced at a price it needed to be produced at to ensure that the war effort was sustained.
