There is a little that we know, like JStaal wanted an increased role and that he turned down a $60M, guaranteed deal. There is a lot that we don't know, like has JStaal made it known behind the scenes that he intends to come to Raleigh? Is he tired of Pittsburgh (and who wouldn't be)? Did he send a top secret message through his dad, Henry, who passed it along to their surrogate son Tripp, that got through to JR?
Tampering...please. This type of behind the scenes stuff takes place at all times, and there is a sibling on the team? Brothers talk you know.
I think JR was trying to make something happen this year and not wait a year. Yes, he could have hung on to Sutter, Dumoulin and the pick and taken a chance. A lot can happen in a year. If JStaal was unhappy in Pittsburgh and JR knew it, he makes a play now and doesn't take the chance of it changing.
The "tampering" could be as little as this:
EStaal knocks on JR's door and sits down. "JR, Jordan is fed up with the Pens and all the Crosby drama and looking at that horseface Malkin. How about saving a little cash to sign baby bro next summer".