Upvote:4
Several issues came together.
Upvote:11
The armistice severely impeded the German ability to continue to wage war:
- They lost their submarines so could no longer counter-blockade the UK
- They lost their battle fleet so could no longer prevent Allied amphibious attacks
- They lost their frontier being forced to abandon territory West of the Rhine (with Allied bridgeheads on the East bank as well)
- They lost their logistics system in that they had to surrender a large amount of railway engines and rolling stock
Beyond that they had no allies of their own, were politically unstable after the overthrow of the Hohenzollern monarchy, and as @o.m. noted in his answer the German army had been defeated in the field and the blockade was taking it's toll.