The purpose of Yuanshi Tianzun's assembly of all Saints this time is to enhance the strength of the Primordial World as much as possible. Since the Buddhist Sect is a part of the Primordial World, a stronger Buddhist Sect equates to a stronger Primordial World.
Moreover...
Xuanqing glanced at Yuanshi Tianzun unobtrusively, knowing that the other had an incarnation serving as Yuqing True King Buddha in the Buddhist Sect.
This second senior uncle plans to open a branch of the Chan Sect within the Buddhist Sect, with Ci Hang, Wenshu, and others being long-arranged pawns in this endeavor.
Although the Three Taoist Sects must inevitably sacrifice some interests in this process, in the long run, the advantages outweigh the disadvantages.
The Great Dao of Chan Sect needs to learn to embrace change to keep up with the times.
During this period, Xuanqing's incarnation, known as Worldly Freedom King Buddha, staying in the Buddha Realm, has also discovered some merits in the Buddhist Law.
