Prosecutors are recommending 0 to 6 month jail time and less than ten grand in fines. I suspect his cooperation has a lot to do with such a small punishment. Not to mention the almost certainty he wore a wire for the feds after being charged.
Hate to be a bubble-buster about the wire thing... It makes sense and I would hope it is true... however, the court papers associated with his (previously secret) criminal trial indicate that he was ordered to "make no contact with any person affiliated with [the campaign]". So wearing a wire and talking to these guys would have been a violation in the court's eyes. It could aslo have been an intentional smoke screen so that if anything done there leaked, it would not look like he was turned.
"hey, it's me, George.. look, I'm not really supposed to be talking to you right now, but I really need to who that was that you met with.... I don't want my story messing you up..."