Why Don’t Business Leaders Assassinate Competitors?

It's called game theory, genius. A genetic algorithm can demonstrate that over repeated iterations, the best way to solve the "Prisoner's Dilemma" problem is to play "nice" rather than "nasty". That is why we don't murder or whatever else outside of fiction, because it is against our long-term self-interest to do so. This is not an issue of ethics. It is just basic game theory. End of story.