The historical Deuns of Dali were not as noble as their wuxia counterparts

In Jin Yong's wuxia universe, the Deun Family of Dali were not only men of royalty, but gallant wulin heroes. From the time of DGSD, Baoding suzerain King Deun Jing Ming, Prince Deun Jing Tsun, Prince Deun Yu, and their associates were highly esteemed as heroes. In the time of L/ROCH, South Emperor Deun Chi Hing and his associates (e.g. Chu Tze Lau, Mo 3 Tung, etc.) were similarly honored within the society of heroes, and were crucial allies of Gwok Jing and Wong Yung in the defense of Seung Yeung Fortress against the Mongol invaders.

History's Deun Royal Family of Dali, however, was not as noble as their wuxia counterparts. Indeed, while Jin Yong portrayed the Deuns as faithful allies of the Seung Yeung defenders, in history, it was the Deun Royal Family who, to preserve their people and to retain ongoing authority as governors of Mongol-occupied Dali, agreed to an alliance with the Mongols to allow the Mongol army to pass through Dali, thereby enabling the Mongol army to besiege Seung Yeung from two different fronts. The Deuns even sent Dali troops to support the Mongol army, and the passage of Mongol troops through the unexpected and relatively unsecured southwestern front is what ultimately doomed Seung Yeung in CE 1269. In contrast to Jin Yong's noble and heroic Deuns, the historical Deuns were less than honorable, at least in terms of standing by their erstwhile Sung allies.

Frankly, I believe from medieval times and before, most anyone who stood a chance of getting to and surviving in a leadership role more or less would be considered cruel and unsavory by 21st century standards.