Amatsu-Mikaboshi said something that triggered something to Grand Mistress Nu Wa as she never really knew why a group of Immortals started slaughtering the Ryujins back then. It was a given that they could have just sealed the Dragon Sealing Statue away and use it when an evil Ryujin wreaks havoc, but they actively used it to kill them. There was only one evil one that committed atrocities, and she never really held the Immortal that killed that one accountable as it was justified.
The Ryujins were like the Daemos as they mainly made sure that nature is stable and that the slaughtering of innocent normal people is not done. They also made sure to have minimal contact with the outside world and only stepping out when they are needed the most. Even the fact that Grand Mistress Nu Wa helping create kingdoms is due to the bad conditions that a place is cursed with.