The 2018 World Scrabble Championship was held last month in London. The champion, 51-year old Nigel Richards, played “groutier” (meaning “sulky”) for the winning 68 points. This was Mr. Richards’s fourth world title in English Scrabble; he also took the French Scrabble title this year for the second time, even though he doesn’t speak French.

If Mr. Richards’s dominance of competitive Scrabble is clear, there is a less noticed but more significant pattern in the game: Since the World Scrabble Championship began in 1991, all...