Assyrian Kings

In chapter 4, Joannes describes in detail the ways in which the Assyrian Kings attained power and exercised power throughout his kingdom. What stood out to me most was the fact that these Assyrian Kings were regarded as almost divine beings, serving the god Ashur and being the chief priest. In addition, he was the commander-in-chief of the army as well as an absolute monarch, requiring absolute loyalty from all his "servants." The King's decision was regarded with utmost importance and no one disobeyed the king. However, what struck me as rather cowardly of the kings was the possibility of a "substitute" king. If the Kings were so highly deemed and were seen as directly serving the god Ashur, how was it possible to have this mighty king replaced by a man in the nobility (or sometimes a worthless prisoner) just to avoid some misfortunes in his reign? Of course this policy was most likely created by the king himself to avoid dangers, but how the nobility and the people agreed to this, seems preposterous to me. If they believed that the king was truly chosen by the gods and required absolute obedience and loyalty, then even in times of peril, the king should be the one taking a stand instead of hiding away whilst putting forth a "substitute" king.