Throughout all recorded history of the known world, there has never been an instance of a divine incarnation descending into the human world.
Many so-called divine incarnations were entirely fabricated by later generations, making far-fetched associations that simply cannot withstand scrutiny.
A legend is a legend, whether treated as a joke, a fairy tale, or something else entirely. However, the appearance of a true divine incarnation in the human world, especially before one's own eyes, could spell disaster rather than fortune for a ruler.
If it were confirmed that Karu is the incarnation of the goddess, with his power and ability to command flowers, he could quickly gain a large number of followers—a real god who can testify to their presence is far more compelling than something insubstantial, which might lead to a mass conversion of other races within the Demon Clan to his faith.
This is certainly not a scene the three Witch Kings hope to witness!