The Pens have to one of the only teams to build so much of the team through trades. It seems like all of the important pieces besides Malkin, Letang, Crosby and Murray were from trades
Not quite. The 2006 Hurricanes weren't far off. Interestingly enough, JR was the GM in both cases. I think the only key guys they drafted from that 2006 Cup team were E. Staal, Ward, Ladd and Cole.
Via trade/UFA (mostly trade) they acquired: Brind'Amour, J. Williams, Recchi, Stillman, Whitney, Wesley, Weight, Cullen, Kaberle, A. Ward, Hedican, Commodore, K. Adams, M. Gerber, Babchuk.
Hard to say "1" trade won that cup for them since a LOT of player were acquired via trade, but as others said, the moves to get Recchi and Weight were key, particularly because it kept other teams from getting those guys AND when Cole went down, they needed the depth.