Although Jiang Yuan True God had previously established a Law oath with Li Yuan, Jiang Yuan True God did so with the mindset of 'give it a try, there is nothing to lose.'
He never truly believed Li Yuan would surely ascend to Heavenly God.
After all, becoming a Heavenly God is incredibly difficult.
What about awakening the Eight-Star Veins? Most direct disciples of Heavenly Gods are of the Eight-Star Veins too, but only a few eventually ascend to become Heavenly Gods.
Therefore, after bringing Li Yuan back to Yuan Country Capital, Jiang Yuan True God gave Li Yuan opportunities... rather than directly bestowing treasures upon him.
He was also observing Li Yuan.
In Jiang Yuan True God's view, if Li Yuan could really become a Heavenly God, then with the opportunities he provided, Li Yuan should be able to rise quickly in both Yuan Country Capital and the Starry Sky Ancient City.