Responses
I think because Princess Blonde has good backing.
And even if the Prince knew, he can't just convict a person with no proper proof for Princess Blonde alter the story that it was because she was used sleeping in silk and not the peas.
Also, the bewitched Maid was the one who took the peas and said she did it on her own volition.
Princess blonde obviously cheats, was caught with proof to boot but still ends up the only one passing even when the prince knew she was cheating
The manga logic is strong in this one