A sudden and dramatic downfall strikes the most powerful ruler in the world, stripping him of his humanity and casting him into the wild. The divine decree is sealed and immediately carried out, driving him away from human society to live and eat like an animal, his body soaked by the dew of heaven [רש״י].
The primary approach among commentators is that this exile and transformation into a beast is not a literal physical change. He does not actually turn into an ox. Instead, he suffers a profound psychological breakdown. Losing his human intellect, he falls into a severe state of madness and deep despair [מלבי״ם, אבן יחיא]. Driven by this mental collapse, he actively rejects human companionship, banishing himself to the wilderness where he adopts animalistic habits and desires [מצודת דוד, מלבי״ם]. This descent into a feral state serves as a direct, measure-for-measure punishment for his overwhelming arrogance. Because he attempted to elevate himself to sit in the dwelling place of God and claim divine glory, he is brought low to live among the beasts [אבן יחיא].
Living in absolute neglect, his physical appearance drastically changes. His hair grows thick like the feathers of eagles, and his nails become like the claws of birds of prey [רש״י, מצודת דוד]. Since he no longer views himself as a human being, he receives no care from others. The constant exposure to dampness and dirt, without any shelter, causes his hair and nails to grow wild and untamed [מצודת דוד, ביאור שטיינזלץ].
Despite his feral condition, he retains his basic human form, which unexpectedly preserves his throne. Because people see him wandering and know he is still alive, his servants do not rebel. His son simply manages the kingdom in his place until he eventually returns [מלבי״ם]. The depth of his psychological detachment is so severe that when he recounts the events, he speaks of himself in the third person. By doing so, he reveals that during his period of madness, his mind was completely disconnected from reality. He did not even feel his own suffering, experiencing the bitter ordeal as if it were happening to an entirely different person [אלשיך].