Answer:
To show that he is not as powerful as he thinks.
Step-by-step explanation:
Tze-Yo-Tzuh was the creator of all things including the monkey king and he was not happy with the monkey king's abuse of power. Tze-Yo-Tzuh wanted the monkey king to live like an ordinary monkey, but the monkey king refused, because he believed that no one was capable of defeating his power.
As a result, Tze-Yo-Tzuh trapped the monkey king under a pile of stones, to show that he was not that powerful.