By far the biggest piece is that WikiLeaks’ relevance has declined over the past several years. When Assange was first summoned to appear in Sweden I think there was an enormous spotlight on him. This might not have saved him from being convicted for the crime he was accused of, but it might have been enough to dissuade the Obama administration from seeking to extradite him. That administration had already expressed concern about the impact a prosecution might have on journalistic freedom, and (at the time) extraditing him on arrival in Sweden would have made both governments look like that were colluding to use a sexual assault accusation as a pretext for political retribution. I’m not saying they wouldn’t have done it: I am saying it would had massive repercussions for the US administration, Sweden, etc.

Instead of facing the charges head on, Assange chose to lock himself in his own prison. Years went by and the public’s interest in him waned. A new administration came to power that had no specific concerns about the press, and saw Assange as nothing more than a criminal. Finally, he decided to intervene in politics in a way that many saw as an intentional effort to affect the election, which damaged the case that he was simply a publisher. Ultimately I think you’re right that this damaged his sympathy with the people who would have been the most vigorous defenders, but the thing is: outside of those people he seems to have no base of support at all anymore.