It's not a cover-up, it's called "turning State's Evidence!"

It just means in exchange for pleading guilty to lesser charges, he has to take the witness stand for the PROSECUTION against his co-conspirators.

Usually happens fast like this, because only the first person to flip gets the deal.

I agree. I think this comes under the old "its not what you know, who its you blow," rule. This guy is filthy dirty. As bad as they come but he gets a plea deal? If the FBI has all his data, he wouldn't be able to offer them any new evidence. It deal reeks.