Historically, the economic effects of military mobilization creates capital in an economy. In the case of WWI this did happen and contributed to the roaring 20’s. The dire situation in Germany was not immediately felt in the rest of the western world. The predecessor of TV was radio, and sales of radios soared throughout the 20’s and led to the development of the modern media which in turn has developed into the information age of today. However, without the wartime mobilization the market for radios may not have existed, and the yellow journalism common prior to 1914 may have remained dominant. Additionally, sales of automobiles did not really take off until the 20’s as well.
Your implication that WWI did not stop imperialism is correct, however, it did destablize it and after WWII it was not viable anymore. In Britain the very symbol of their imperial might was their navy, yet after WWI they were forced to scuttle 2 dozen battleships because they couldn’t afford them anymore. As for free trade I should have clarified that this has happened only after WWII. In fact the primary causes of WWII in both Europe was the lack of free trade which stunted Germanys post WWI economy, and kept Japan a second rate economic power. However, after WWII Japan got the access to foreign markets which was its primary war aims to begin with.
On a side note the Allies did not destroy any German infrastructure after or during WWI. In fact Allied troops never stepped foot on German soil during the War. If anything the French had a bigger complaint against the Germans, and a ‘right’ I might add to demand reparations since much of their infrastructure was damaged because the entire war was fought on their soil. The turmoil in post war Germany was caused by the rapid development of Democracy in their country which had been violently suppressed since 1848. It’s quite analogous to what is currently go on in Iraq where a country that has been repressed for so long is finally waking up to democracy. In Britain and the US this was a more gradual process, but in France democracy caused an equal amount of turmoil.