It's certainly not because they did any personal research on Hillary, or read any of her books, or did any other kind of delving into her life which would have shed more light onto who she really is.
I didn't realize that journalism was reading self written memoirs and taking it as fact.
You can gain insight into people by reading things they wrote. They aren't likely to make a claim that can easily be debunked. That's my experience anyway. I like to read from a variety of sources and make up my own mind about a person.