First problem can be that they lost a lot of their territories. They had to give away all their colonies and also parts of their land to others which caused a huge problem since those territories were inhabited mostly by German people who didn't support these new governments. They supported German rulers and wanted German governance so an independence struggle was inevitable.
Second can be that they were financially ruined. Because they lost all colonies and their country was devastated, they could not make any money at all. This was combined with the fact that their war reparations were so huge that they couldn't pay them off, it more or less made the whole country bankrupt. The people were enraged by this and didn't want to support such clauses.
Third was that the people felt humiliated. Because of everything that happened because of their government, they felt that they were being punished to severely for something that they didn't do since the government then was a monarchy. Their anger started rising and when Hitler showed up and talked about this, they started supporting him so it led to a huge rise in extremism.
The least important reason for the end of the Western Roman empire is the natural disasters. You can consider this as the least important because there are<span> other major events that happens which leads to the fall of this empire.</span>
