All I need is a "magic bombardment," following the wisdom of my ancestors, to declare "it's the woman's fault, let the Great Witch Woman report to the River Lord, and find a better girl to sacrifice the next day."
Throwing the shamans, village elders, and local tyrants into the river, eliminating the chief villains one by one, would easily solve the issue, while giving the officials from the Fishing Tax Office a taste of "King Huai's wisdom."
It could be accomplished smoothly and effortlessly.
In the end, it's all utter feudal superstition! The local elders took the lead in charging forward, sacrificing their own granddaughters to the River God, demonstrating devotion, "leading by example."
Reason, where can it be found?
With normal logic, such matters are indeed difficult to handle. Centuries of indoctrination have left everyone firmly convinced. If it happens that two sacrifices "work," it can directly imprint the ideology.
