Rod knew Horus would think this way. The awakening of the Human Demon was because he recklessly broke the seal.
In fact, they should have anticipated it earlier. The scale of the Underground City, the lake of corrupted humanity never seen before, all indicated that there might be a huge danger lurking. However, a series of victories made them lower their guard, but this mistake was made the moment they stepped into the "anomaly".
It can be said that when Rod used the "Heavenly Sphere Clock" to find a way into the "anomaly," the ending was already set; therefore, in the prophecy, this crisis was triggered by him.
However, judging by various signs at the time, even if he didn't go, the Human Demon would surely awaken, and by then, they would have had no preparation at all.
The consequences of such a powerful monster suddenly attacking Trolian are unimaginable... so this isn't a mistake, Kai didn't die in vain; his sacrifice was meaningful.
