As far as I remember, Ellsberg was a true believer for a long time and originally wanted the information (not all of the papers) out so America would double down on VN. He thought it was still winnable. He moderated at some point in the process. Sheehan wasn't going to wait for his navel gazing and made him a progressive hero.
Absolutely. However, is it bigger than every story you're ever going to run? Because if I'm a potential source, and I see that you're rag is fine with sending sources to jail for a source, I'm not going to talk to you. Worse, if I'm a guerrilla group with an embedded journalist, I may very logically decide that they are a threat.
I don't recall the documentary I watched, but the impression I got was that Ellsberg needed or wanted Sheehan to make the call that he couldn't bring himself to make.