My first thought. He knows where the Clintons "hid the bodies".
Maybe he was asking for a few favors in exchange for his silence - because he also knows where he hid the documents.
It would be a thrill to find out those documents have now been recovered!
As I recall there really wasn't too thorough investigation into this thievery. Was it ever determined precisely which documents were taken and what they pertained to? That could be quite telling.