Yes, you've made a good observation!
Did the King realize that there is no magic stone in the soup? He
was rendered irrelevant the moment he was disposed.
For more than 1000 years, the invisible magic stone ruled the
Kingdom.
The King was long dead and his original memoirs burnt down. If not
for some copied versions safekept by the Kingdom of the Invisible
Magic Pearls, we would not know what he knew.