There's a reason why it exists.
If fennec foxes were able to survive in the desert for so long, they must have their own tricks up their sleeves.
For a person that is used to a comfortable, safe life, when danger suddenly dawns upon them, they would usually first pause, hesitate, their brain would short circuit, or would try to see what exactly is the danger first before deciding whether to fight or flight. But, by then, it's often too late.
The fennec fox had skipped through the whole hesitation period, and at the moment that Fina and Famous and jumped out, or when Zhang Zian had lit up the torchlight, they had shot out reflexively, running first before anything else.