Why did nations practice economic nationalism if this policy only prolonged the depression?

Answer: Economic nationalism implies an ideology that favors state interventionism over other market mechanisms.

Explanation:

Economic nationalism opposes or at least advocates restraint on free trade. Economic nationalism favors the stimulation of industrial production at the state level, as proponents of this policy argue that industrial production reflects on all other branches. When we talk about the economic depression that was current in the 1930s, economic nationalism was not the main factor that led to the crisis.

Hoover began pursuing some form of economic nationalism by placing massive tariffs on foreign products. The president did not do so because of the spread of economic nationalism but wanted to protect the domestic economy. This has led to countermeasures by other countries, which has further aggravated the financial situation. Therefore, pursuing such an economic policy is not advisable, and the developed economies of the world do not seek such a system.