Why do people believe humans are animals?

Humans, or the species going under the scientific name of Homosapiens, are primates, closely related to Chimpanzees and other similar beings, which belongs to the class Mammalia, or what was called mammals in simpler terms. As you may have learned before, mammals belongs to the animal kingdom. Therefore, humans are a subset of animals.

if you see a monkey who has human intelligence and can speak would you think its an animal?

This stance is called Animalism in Philosophy. I subscribe to it. There is no evidence to the contrary.

Ehhhhh ???? Wtfv