He published evidence of political corruption. It's a good thing he did it too so that US voters could make a fully informed decision about the candidates.
He published altered and forged documents alleging corruption, where said documents were provided by the Russian intelligence agencies for the sole purpose of influencing the US presidential election.
And Assange, knowing this, attempted to coordinate the release of these falsified documents with the Trump administration. While also prohibiting Wikileaks from publishing any negative documents about Trump.