I always admired Karl. Here you have a guy who has a need to find truths. He's not satisfied to accept the lies society tells us to protect us from the darker side of things. He goes out there and finds out what, often leading to his discovery of the monsters. And his search for truth leaves him open to it and to accepting what he finds.
He's not a macho hero. He would rather someone else fight the monsters, as shown many times in his trying to get the police or others to believe what he knows. But when they don't, he steps up and does what needs to be done.
Much like Peter Falk was Columbo, Darren McGavin is Kolchak, and no one can replace him. Some people are so identified as their character that no one could ever really work in the role. The remake of Night Stalker just proves that point.
Actually they could just as easily have called the series The Kolchak Papers because of all the stories Karl could have had on file but never printed until one day a book could be published...maybe years after he died.
Actually, Jeff Rice's original title for the novel was The Kolchak Tapes