The relationship between the King of Shang and the feudal lords was not as good as one might imagine.
After all, this was not an age of unified rule, and the feudal lords were not entirely subordinate to Great Shang.
The lords largely retained considerable autonomy. Although the King of Shang held absolute control over the royal domain centered on Chaoge, his control over the lords was relatively weak. He differed greatly from the monarchs of later ages; in fact, he was better described as the leader of an alliance between the inner and outer domains.
Strictly speaking, each lord ruled a semi-independent regime. Their relationship with the king was not entirely one of superior and subordinate, but roughly that of tributary states and a suzerain, only with closer ties.
This was true in history, and it was true in the novel as well.
For example, in the novel, King Zhou fabricated charges and executed Jiang Huanchu and E Chongyu. Their sons rebelled without another word, without the slightest hesitation. To them, the King of Shang killing feudal lords-and lords of the Four Garrisons, at that-was going far beyond the pale. He had no right to kill them at all. It was utterly intolerable.
In other words, in the lords' eyes, the King of Shang could not actually convict them of a crime unless it was something truly grave, such as rebellion.
That was why Ji Chang plotted to overthrow Shang. His father had died such an unjust, humiliating death, imprisoned by the King of Shang and killed on trumped-up charges. Had Di Yi, who later succeeded to the throne, not married his younger sister to Ji Chang to secure peace, Ji Chang would already have rebelled.
Even so, the other lords had laughed at him for years.
Precisely for