Reasons triple alliance countries were upset after ww1

Germany was upset because they felt that they had been humiliated at the treaty of Versailles. They were forced to abandon parts of their territory, pay for war reparations for most of Europe, and were forced to abandon any military practices that they had in plans and to destroy weapons and similar things. Their economy was basically ruined and their people had to lie in extremely difficult conditions

Italy was upset because it had fought on the side of allies in world war 1 which was the winning side. Italy was ravaged by the war but they felt that they weren't given what they were promised so their participation on the winning side didn't really give them anything that the other winners got. This caused an outrage and people started supporting those who were against the other European powers.

Austria Hungary was upset because it lost all power that it had. The country itself was split into numerous smaller countries which were nowhere close in power to what they had before world war 1. Some of the successor states lost as much as 70% of their territory because of how the powers were shifted and this made Austrians angry.