This then was the situation, and while everyoneis insight grew and the people stirred more and more and everywhere autonomous thinking and acting arose, the king came in the guise of the man with the golden beard and tested the ministers and tested his son, so that everybodyis abilities could be compared and judged properly.

“It was part of his plan to be caught; but the ministers and their trustees should have the opportunity to see that there was more to the man with the golden beard than just drawing the milk and being a good exhibit.
After all he proved that he ruled higher powers - which is why they could not catch him in the beginning.