There actually is what I believe a credible alternate explanation to Wikileaks supporting Trump, and it's that Wikileaks (or perhaps just Assange) is fighting for relevance, and is willing to be the obvious pawn of others to keep that relevance. What if it's not Wikileaks that's drip-feeding the information, but the source itself? One would think Assange would be smart enough to not promise what he hasn't already gotten hold of, but perhaps he agreed to a release schedule before getting all the information, and is following through on his promise. Not that I think that excuses being a pawn for what is most likely a state actor trying to meddle in the national election of another country.

Neither case really paints a good picture of Wikileaks as an impartial journalistic organization.