Why it worked
The video uses a common internet trope of a small, cute animal being chased by a larger, more menacing creature, but with a humorous and unexpected twist of the 'monsters' being made of fruit and the 'hero' being a large, anthropomorphic dog who eats them. This combination of cute, scary, and absurd elements is highly shareable and engaging.
Summary
A chihuahua is chased by fruit monsters (watermelon and mango) in a forest. A large pitbull dog then appears, having eaten the fruit monsters, and reassures the chihuahua that it is safe.