He could've let him die. Maranzano would've remained boss, there wouldnt of been a commission and Lucchese wouldve been passed over in favor of Joe Bonanno due to his closeness to Maranzano, something Lucchese didnt have. Its not an example of power, and at the same time while you say "without Lucchese Luciano wouldnt of became boss", at the same time without Luciano, the American Mafia would've went a totally different route throughout history.