In the short video, the Little Mermaids drove away the invaders, but what they were met with was not a retreat, instead, a gathering of more powerful artillery attacking the Mermaid's domain.
Mermaids are a strong and dangerous race, and allowing such a powerful race to exist poses a danger to humans. Destroying them before they attack humans is the most thorough method.
Originally, among humans, differences in skin color classified them into different races, leading to discrimination based on those differences, eventually intensifying into the root cause of wars.
The wars on land came to an abrupt halt because the might of the Mermaid Clan was formidable, causing the previously warring humans to unite, hand in hand, different races collaborated to attack the mermaids.
