Based on the classic story "Hilsa Fish," the king stopped talking about Hilsa fish because:

• He challenged his courtiers to stop anyone from talking about the Hilsa. The King was fed up with everyone talking about Hilsa fish, due to the season.
• Gopal successfully achieved the challenge. Gopal managed to buy a Hilsa, carry it through the town to the palace, and speak to the King without anyone mentioning the fish.
• The King admitted defeat. He remembered the challenge and congratulated Gopal on his cleverness. Once the challenge was complete, the topic lost its importance.

Therefore, the king no longer talked about Hilsa fish because the challenge was over, and the point had been made.