Moab's devastating fall comes as a direct consequence of its overwhelming pride. The collapse of the nation unfolds through vivid imagery that captures a complete and total loss of authority and strength [ביאור שטיינזלץ]. The destruction of the kingdom is understood through two distinct elements of its former power.
The first element focuses on the government and the monarchy itself, symbolized by a horn that is entirely cut off. Just as a horn serves as the highest point on an animal's body, a royal government stands elevated above the rest of the nation [רד״ק]. Severing this peak signifies the absolute end of Moab's political rule and sovereignty.
Beyond the loss of its ruling body, the collapse extends to the practical force that kept the kingdom standing. This practical strength is represented by an arm that is broken. The arm stands for the physical and military might of the nation, encompassing its ministers, its soldiers, and its fortified cities. This executing force is what originally gave the king and his people their security and power. Shattering this arm means the complete destruction of Moab's military capabilities [רד״ק, מלבי״ם].