He was literally tweeting up until a few days ago. What makes you think he'd need the press to "unveil" anything "they" "don't want him talking about"?
No one was paying attention to his tweets. He'd get a lot of attention in an extradition.
The message was already sent: you can't flee from the IRS once you are a target. Showing you're not afraid to kill enemies isn't nearly as chilling.
Prisoners dont get to talk to press all that much. You are 100% of time under controll. And having him in prison for long sends even better message then maybe-murder-maybe-not.
What high-level conspiracies was he supposed to have been a party to, that he could have leaked?