‘The same hour was the thing fulfilled on Nebuchadnezzar, and he was driven from men, and ate grass like oxen, and his body was wet with the dew of heaven, until his hair was grown like eagles' feathers, and his nails like birds claws.'
The allowing of nails and hair to grow excessively, the latter becoming matted and thus like feathers, and seeking refuge away from people, and willingness to face the discomforts of nature, is not unknown with certain stages of extreme manic depressive illness, hidden in the modern day by nursing care. There is nothing here that is not typical. And he was the supreme king. No one would dare to interfere, especially as they would see him as afflicted by the gods. They would indeed be in awe of him. So was he allowed to do as he pleased.
But it was probably hushed up. It was better for the peoples not to know. (Although rumours would inevitably spread). And who would know how soon the gods would release him so that he could then vent his anger an any who took advantage of the situation? Thus his sons, eyeing each other, and his chief ministers, some clearly extremely loyal, would be in a continual quandary as to what to do, and Daniel in his honoured position as master (Rab) of the wise men and chief governor of Babylon would have a powerful say in holding things together. It may well have been largely his influence that preserved Nebuchadnezzar's throne.
No doubt any suggestion of including this in inscriptions was severely crushed once Nbucahdnezzar had recovered. It was one thing to circulate the rulers of the empire as a temporary measure to quash rumours, it was another to pass it down in history. But there is some confirmation of this experience in words from the writings of Abydemus, quoted by Eusebius, which cites Nebuchadnezzar as prophetically wishing, when ‘possessed by some god or other', exactly this kind of fate on another (‘a Persian mule' i.e. Cyrus), ‘O that -- he might be carried across the desert, where there are neither cities nor foot of man, but where wild beasts have pasture and birds their haunts, that he might wander alone among rocks and ravines'. He is then said to have disappeared from the city. This would well fit in with a period of known ‘possession', i.e. mental instability, and may well have arisen precisely because Nebuchadnezzar was known to have had exactly such an experience connected with his grandeur and was now portrayed as wishing it on another.
Another Babylonian inscription discovered by Sir Henry Rawlinson from the period of Nebuchadnezzar reads, ‘For four years the seat of my kingdom in my city -- did not rejoice my heart. In all my dominions I did not build a high place of power, the precious treasures of my kingdom I did not lay out. In the worship of Marduk my lord, the joy of my heart in Babylon, the city of my sovereignty, I did not sing his praises and I did not furnish his altars, nor did I clear out the canals.' He must clearly have been ill in a fairly severe way for this to occur.