Su Changxing realized the other party wanted to persuade him, but Huang Biao's argument also made him think it wasn't fake; he truly couldn't leave the Donglin Region.
Why is this?
Most likely because of his position; he accepted powers from the heretic, so he was repelled by the rules.
This was his choice, and now it was the consequence of his choice.
However, Huang Biao's words also gave him some other speculations; Huang Biao himself did not have any foreknowledge ability, just like Zhu Wenwu, they both had additional memories.
Moreover, in Huang Biao's memories, the world's trajectory was completely different from Zhu Wenwu's. Su Changxing did not die in the great battle of Donglin City but survived.
But this triggered the collapse apocalypse; this apocalypse appeared because of him, and he was the catalyst for this apocalypse, also known as the cause of the apocalypse.
