The FBI wanted him extradited. He didn't want to be extradited. So there was going to be a hearing about whether the FBI got what they wanted, or Dotcom got what he wanted (or some court-mediated compromise, but that seems unlikely in this case). Kim negotiated with the FBI so they no longer disagree about whether he will be extradited, so the hearing is no longer required.
He is going to the US to stand under US law and this was an FBI initiated and led operation, with the other organisations giving what the FBI terms "substantial and critical assistance", so as far as I can tell this means that outside the US, only the NZ police have assisted in any operational role. "Critical assistance" could even just mean other organisations advising them that it was an appallingly bad idea, depending on how cynically you judge the content of government documentation.
