But...

You guys know a lot more than myself about historical mafia organizations, bosses, and hitmen. However I have read that modern organized crime both looks for actual psychopaths as hitmen and trains those who aren't into desensitizing them to murder and torture. As did many regimes in the past. So the line may be going thinner at least from that side. Obviously born psychopaths are not the ideal organized crime enforcers as they are not very interested in following orders.

You are right that serial killers are for the most part not glorified and mafia bosses and hitmen for the most part are. And that the film (and other media) depictions of both, either based in reality or fully fictional, clearly show this.