How can a film maker justify making a major film-narrative out of the short story "The Most Dangerous Game"?
Your question is somewhat ambiguous, but I am reluctant to change it too radically because I may not understand it correctly. You seem to be asking how a filmmaker could turn "The Most Dangerous Game," a fairly simple short story with only two important characters, into a full-length motion picture. It is true that short stories often fail to make good full-length films, but "The Most Dangerous Game" has so much visual potential that it was actually made into full-length films three times.
The first time was in 1932. It starred Joel McCrea, who was a star in those days, and included a role for a woman, who was played by Fay Wray, the actress who had spent so much time being held in King Kong's hand in the original version of that film. Then the story of "The Most Dangerous Game" was used for A Game of Death in 1945 and again as Run for the Sun in 1956.
The story naturally divides itself into a number of good scenes. First there is the foreboding night scene aboard the yacht. Then there is the hero swimming in shark infested waters. Then there is his amazed discovery of a mansion on the island. Then there is his realization that his sinister host is hunting humans, and subsequently his realization that his host intends to use him for his fiendish sport. This is only the first half of the story. The actual chase provides plenty of suspense and plenty of opportunities for good cinematography. The story itself ends abruptly, but a motion picture version could include a more violent encounter between the two adversaries, as is done very effectively in the 1932 version of the film.
Admittedly the story is melodramatic and the two characters are stereotypes, but it is a good yarn, similar to another good adventure movie, The Naked Prey (1966).