If we're going to quote passages from her journal entries about the Hickman thing, let's quote the rest of them that more fully illustrate what she was thinking at the time. I haven't read or talked about this particular stuff in forever so I had to look it up.
"[My hero is] very far from him, of course. The outside of Hickman, but not the inside. Much deeper and much more. A Hickman with a purpose. And without the degeneracy. It is more exact to say that the model is not Hickman, but what Hickman suggested to me."
"Yes, he is a monster - now. But the worse he is, the worst must be the cause that drove him to this. Isn't it significant that a society was not able to fill the life of an exceptional, intelligent boy, to give him anything to out-balance crime in his eyes? If society is horrified at his crime, it should be horrified at the crime's ultimate cause: itself. The worse the crime - the greater its guilt. What could society answer, if that boy were to say: 'Yes, I'm a monstrous criminal, but what are you?'
"This is what I think of the case. I am afraid that I idealize Hickman and that he might not be this at all. In fact, he probably isn't. But it does not make any difference. If he isn't, he could be, and that's enough. The reaction of society would be the same, if not worse, toward the Hickman I have in mind. The case showed me how society can wreck an exceptional being, and then murder him for being the wreck that it itself has created. This will be the story of the boy in my book."
Sounds to me like it was largely just a real-life situation that was a jumping-off point creatively to something else. I expect the Hickman case caught her imagination because it was what happened to be a big news event at the time. Artists find the seeds of ideas in seemingly unlikely places sometimes, and it seems pretty clear she realized she was projecting qualities onto the guy he didn't possess in the process of forming a fictional character. Looks to me like what she took away from it all was basically, what if a man wasn't a murderer and his "crime" was standing against the masses and asserting his individualism in a way people didn't like, would society vilify and despise him just as much? Possibly the early seeds of imagining a Howard Roark type character.
These are journal entries made when she was very young, by the way, and still grappling with the man-versus-the-masses ideas that would be incorporated into her novels many years later. It's a bit like you going to see Silence of the Lambs when you were in college, developing a short-lived fascination with Hannibal Lecter and writing in your journals that it got gears turning in your head about human psychology which later led to you writing books that have nothing in them that would suggest you venerate his kind...only to have people digging up your old journal entries decades later to claim you're a sociopath who admires murderers who eat their victims in order to discredit you as a writer.
I'm not Rand's public defender. It's been over a decade since I read any of her books and this is probably the most I've talked about her in years. But damn, what a silly thing for people to continue perseverating on and trying to use as proof incontrovertible of Rand's evil depravity rather than attempting to provide a logical refutation of the ideas presented in her writing as a fully-formed adult who had gotten her thoughts together.