How did Old Man Sheun lose to Seung Gwoon Gum Hung?

At the beginning of SENTIMENTAL SWORDSMAN, RUTHLESS SWORD, the ranking of the top three positions in wulin were 1). Old Man Sheun the Storyteller, 2). Seung Gwoon Gum Hung, and 3). Lee Chum Foon. In some 24 hours or so, # 2 had overtaken # 1's position, but before the new # 1 could even get comfortable in his new top-ranked position, he lost to the former # 3.

We all know the circumstances that led to Lee Chum Foon defeating Seung Gwoon Gum Hung, but how did Seung Gwoon Gum Hung defeat Old Man Sheun? Had Sheun's age (and lesser stamina) finally worked against him during his struggle with SGGH? Had SGGH improved greatly since the previous ranking? Were Old Man Sheun overrated and SGGH underrated all along? How did it happen?