Blowing the whistle is not effective when you simply publish a blog post somewhere. It requires theatrics to establish credibility, interest, and to reach the right audience in a way that can't be ignored.
The first time he did it, well it was not effective.
It's not like people were not informed enough about war crimes. The Abu Grahib dossier had come out 3-4 years earlier.
People perceive this sort of stuff as far away, don't want to look at it or just simply block out the information because they want to believe whatever they want to believe.
Whistleblowing is ineffective to change the way a system operates. It solely make the system cover up better, and achieves the goal of having some heads roll (more often than not the responsible people for security and info compartmentization)
Your last paragraph didn’t happen for any recent major leak - Wikileaks war crimes, Snowden. Hell did it even happen with the Panama leak? There was no large change towards transparency. The little I’ve heard, the same usual tax shelters and money hiding continued.