If one takes the view that Clinton and her cabal have engaged in heinous crimes for the last 30 years, then its a simple matter of the lesser evil. I really think he feels this way, as do many supporters of Wikileaks.

Plus, there's the whole "drain the swamp" thing that Trump promised, as an outsider, to execute. So I don't think its so much that Wikileaks decided to become pro-R, just that Trump very definitely had/has the opportunity to shake up the incumbents and alter the status quo, and this is also in alignment with Wikileaks' stated goals. So, there's that.