The Treaty of Brest-Litovsk of March 1918 was very much a Carthaginian peace with the German-led Central Powers demanding exorbitant amounts of resources, territory, and money from the Bolshevik regime. Yet much of this bounty really did not reach the German homefront; there were shortages of coal and food despite the Treaty's promises. The long and the short of it is that there was no real way for the Germans or their allies to collect on the Treaty in the hurried months between March and November 1918.
The Treaty presented two interrelated problems for the Germans. Firstly, the very scope of the Treaty required a vast number of troops to enforce it. Ober Ost maintained troop levels of around a million men on the Eastern front to keep order and maintain the German presence. This was partly because although the Germans had signed an agreement with the Bolsheviks, they did not exactly trust them to uphold their end of the bargain. Moreover, many of Ober Ost's officers maintained dreams of expanding Brest-Litovsk into a permanent Germanic empire on the former Russian Empire's western frontier. This was an ambitious view of German hegemony that went beyond even the harsh strictures of Brest-Litovsk.
What these eastern dreams of Ober Ost meant was that a good deal of the harvested food and resources ended up being consumed by the German troops left in the East. Finished war materials often ended up in the hands of Germany's would-be Eastern lieutenants or even some of the emerging White forces rather than feed them back to the Western front. Ober Ost may have collected vast amounts of food, something Ludendorff was keen on publicizing during the war and after, but only a trickle ended up back into Germany itself. Shortages of rail stock meant that getting requisitioned foodstuffs and other materials back to Central Europe was difficult. Some strategic materials like oil ended up in German factories or in the rations of German troops, but the average German civilian saw little of this peace dividend.
Part of the the reason why these occupied territories could not deliver the goods was directly related to the political situation created by Brest-Litovsk. Lenin gambled (correctly, as it turned out) that Germany would not be able to harness the surrendered resources or gather them. One of the reasons why Lenin was able to push through the Treaty was that he knew that the Bolsheviks were ceding areas and resources they did not have effective control over. The Russian Revolution had accelerated a process by which the Western provinces' government effectively disintegrated. The lack of any central authority contributed to a general collapse in the local economy and a return to almost subsistence or barter economies. The absence of a stable economy, or even a shaky one, meant there was little available for the Germans to collect. Rather than halting this process, Ober Ost's ambitions added further fuel to the fire. The Germans supported various factions in the hopes of making them lieutenants in the immediate future, but this only created more civil conflict. Brest-Litovsk may have ended hostilities between Russia and the Central Powers, but it did not end the violence in these regions.
The Germans would have needed both peace and stability in the Western provinces in order for Brest-Litovsk to have delivered. But the very nature of both the Carthaginian peace terms as well as the politics that created them precluded this. The Treaty did buy psychological benefits for the German homefront, but flagging German morale was still incredibly brittle following the Hunger Winter of 1916/17. Reports of victory in the East restored faith in the war effort, but Brest-Litovsk needed to be followed up by a similar victory in the West. Brest-Litovsk arguably acted as a greater material drain on Germany's war effort than a boon.
Sources
Chickering, Roger. Imperial Germany and the Great War, 1914-1918. Cambridge: Cambridge University Press, 2014.
Herwig, Holger H. The First World War. London: Bloomsbury Publishing, 2014.
Liulevicius, Vejas Gabriel. War Land on the Eastern Front: Culture, National Identity and German Occupation in World War I. Cambridge: Cambridge University Press, 2005.