Heavenly Court was the center of the Primordial World's operations. After Di Jun and the other members of the Witch Clan had fallen, Dao Ancestor Hongjun had acted under the Heavenly Mandate to establish its authority over the Primordial World. Haotian was enfeoffed as the Jade Emperor, nominally the Primordial World's Great Heavenly Venerable.
Though Primordial Saints were supreme in the Primordial World and the various Sects of the Saints flourished, Heavenly Court's standing beneath the Heavenly Dao was unshakable. Even when oppressed by the Sects of the Saints, Haotian Jade Emperor had to honor the Saints' decrees, but that could not change his claim to orthodoxy.
The Netherworld governed life, death, and reincarnation, while Heavenly Court oversaw the Primordial World's workings. Both were places of fortune and merit. The Sects of the Saints vied for fortune, and the Saints needed to place their disciples in these positions to secure legitimacy and control over the Primordial World.
The disciples of the Sects of the Saints had previously entered the Netherworld and become the Five Directional Ghost Emperors beneath Great Emperor Fengdu, who presided over the reincarnation underworld. That had set a precedent. Now that the Heavenly Dao had ordered them to discuss the exalted positions in Heavenly Court, the Saints simply went along with it.
Among the Primordial Saints present, Jun Tian Daoist kept to himself in Jun Tian Realm and had yet to establish a Dao Lineage, so he did not recommend anyone for the Five Elders of Heavenly Court. Saint Pingxin presided over the earthly Dao. Though she hailed from the Witch Clan, the Witch-Demon War had left both clans guilty of great sins, making it impossible for the Witch Clan to ascend to Heaven.
As for East King Duke and Tai Zhen, Queen Mother of the West,