The Dong Family had the backing of the Lu Clan from the Imperial Capital.
As for the Song Family of Jiangbei, they had previously aligned themselves with the "Anti-Li Alliance," an organization established by the young master of the Imperial Capital's Lu Clan.
Although for some unknown reason the Jiangbei Song Family had subsequently drifted apart from the Anti-Li Alliance, they still maintained enough ties through that past connection to at least have a seat at the table.
Chapter 234