The goodreads description of how the Wisest king in all the land learns from a wandering student of philosophy the importance of silliness
is rather misleading, as the whole point of this story is that the king is not wise at all; he's a pompous moron who thinks he's smart because his sycophantic courtiers flatter him and never point out his stupidity. Oh, and also because he has honorary doctorates.
Since he is the wisest of men, King Kilian assumes his daughter must be the wisest of young ladies, and therefore deserving of the wisest of husbands. But nobody is wise enough! Poor Princess Zinnia can't get any action. When a random college-drop-out hippie type in a floppy hat trespasses into her garden, she is so desperate to get hitched and escape from dumb-ass dad that she quickly agrees to marry him, if only he can find some way to trick the King into allowing it.
I won't go into the unlikely ruses by which the King is eventually lured into a crate and locked up, but I will say that they demonstrated not the "importance of silliness" (i.e. the positive value of play and imagination) but rather the importance of not being a self-important wind-bag without the slightest vestige of common sense.
Perhaps they all lived happily ever after.