I don't think the journos were lazy, and I don't think there was an organisational failing. The Guardian, in particular, evidently fell out with Snowden and his collaborators; they turned on him. I assume that was coordinated with Washpo and Spiegel. That is: I think there was a decision made, to stop publishing information from the Snowden trove.

I don't know what the reason for the betrayal was. I'm pretty sure Alan Rusbridger knows though. He resigned as Editor-in-chief shortly after these events.

I don't get why whistleblowers rely on newspaper publishers to unpack their leaks for the public; it's not as if the press are known for either their honesty or their scruples.