"The bell tolls still must be silenced by the one who rang it."
This situation was orchestrated by the Tathagata, so only he could resolve it; none of the other Immortals and Buddhas were qualified to intervene.
Thus, Jiang Liu knew well, that to save Gaoyang, he had to seek Buddha himself.
However, from the perspective of the Buddhist Realm, they would probably prefer Gaoyang to perish so that he could quickly embark on his Journey to the West. What bargaining chip then did he have to make demands of the Buddha?
After much deliberation, Jiang Liu felt he had no choice but to use himself as the bargaining chip.
In times of having nothing, one can only gamble with oneself; it has always been so throughout history.