But there was an election around the corner, they can't be bothered with any of that.

Why is that better than releasing all the emails at once?

Why do they get to decide what's "pertinent"?

DNC misconduct etc. would have been reported by traditional organizations. I think people wonder why it was good that Wikileaks released Podesta's iCloud password, his risotto recipe, doctors appointments of random staffers, and so forth.

For the same reason that if you found yourself with access to someone's diary that you thought might be guilty of wrongdoing, you might convince yourself to look through it possibly with a lawyer friend and report on if anything illegal went on, but you might shy away from publishing the whole thing online "just in case".

One option at least pays lip service to legal and ethical considerations.

I wonder if how Julian releases the primary source material is in line with his scientific journalism [1] practices.

[1] https://en.wikipedia.org/wiki/Scientific_journalism

A news organization has a responsibility to present information in an informed manner in order to prevent misunderstandings and misrepresentations. Wikileaks' purpose was to paint an impression of widespread wrongdoing despite any hard evidence. Dumping a bunch of irrelevant emails all at once aids misrepresentation.