Well, the monkey in the 'nope true story' could have multiple significances. It could be a plot device to drive the story forward. Imagine if the monkey's actions or presence are what start the chain of events in the story. It could also be a cultural or historical reference. Maybe in the real - life event that inspired the story, the monkey had a particular meaning in the local culture or history. And in the movie, it is used to add depth and authenticity. Another aspect could be that the monkey represents the primal instincts. In a horror - themed 'Nope', the monkey could be a manifestation of our primal fears, something that is wild and unpredictable, much like the nature of horror itself.
The monkey could be a symbol. In many stories, animals can represent different things. Maybe the monkey in this 'true story' represents chaos or the unexpected. Since 'Nope' is a horror - type of movie, the monkey might be a source of the horror, like it brings in an element of danger or the unknown.