Why did disasters continue after Li Shimin ascended the throne?

李世民登基之後，朝廷下令大肆捕殺水族，導致龍宮裡的蝦兵蟹將越來越少，涇河龍王得知後大怒，於是決定水淹人間三個月以示懲戒
After Li Shimin ascended the throne, the imperial court ordered the mass killing of aquatic creatures, which resulted in fewer and fewer shrimp soldiers and crab generals in the Dragon Palace. When the Dragon King of Jinghe learned about this, he was furious and decided to flood the human world for three months as a punishment.