Looking at this video it looks like they were doing really well in 1918:
https://www.youtube.com/watch?v=TVJqRVKmivg
There was no longer an Eastern Front against Russia. It looks like they just gave up even though they still had so much territory. Unlike WW2 the fighting didn't reach any of the civilians in Germany or Austria/Hungry so they could have kept going for victory. Did they predict that the USA would eventually bring in too many numbers for them to be able to defeat the allies?