It's important to notice that he's not been charged for publishing those materials. He's been charged for giving instructions to the hackers about targets and contents, like a lider of the hackers. So, it's not a leak, it's a content obtained illegally through a series of crimes.
This is something journalists do all the time. If a source comes to you, even with illegally obtained materials, it is normal for a journalist to ask for more, that's their job.
People doing something "all the time" in one jurisdiction doesn't magically make it legal in a different one.