With their odd genetics, there is very little genetic diversity in the species, and their ease of taming I have often wondered if they were not specially bred as pets by some long gone civilization who then managed to survive in the wild after that civilization fell.
Cheetahs are supposed to be the easiest of the big cats to train and tame, and the best suited for human companionship-more doglike than the other big cats-in ancient times, the Egyptians and others kept and supposedly bred them to hunt game, just like they did with hounds-maybe some of that affinity with humans still lurks in their DNA...
https://en.wikipedia.org/wiki/Russian_Domesticated_Red_Fox#Initial_experimentation
The retention of juvenile traits is the key.