Sullivan deserves some credit, but he also had good timing.
First time Penguins won, they were unsustainable, b/c of the divergence of ages:
Gonchar (34), Scudari (30), Gill (33), Eaton (31), Guerin (38), Cooke (30), Fedotenko (30), Satan (34), Adams (31)
Malkin (22), Crosby (21), Letang (21), Staal (20), Talbot (24), Kennedy (22)
They only had 99 points that year, then got hot in the playoffs, but the depth aged and they couldn't add new talent fast enough.
They added Neal in 2010-11, Niskanen in 2011-12, Sutter in 2012-13, Maata in 2013-14, not enough, so they resorted to trades and FA in 2014:
Hornqvist and Spaling for Neal in 2014.
Perron for 1st rd pick in 2014
Comeau FA in 2014
Downie FA in 2014
Erhoff FA in 2014
Still not enough, so more moves in 2015:
Dumoulin had come up for the 2014 playoffs, Sheary, Rust & Kuhnhackl
Kessel & 2nd for Spaling, Kapanen (1st 2014), 1st 2015 and 3rd
Bonino & 2nd for Sutter & 3rd
Schultz for 3rd rd
Cole for Bortuzzo & 7th
Hagelin for Perron
TDL Daley for Scudari
So why Sullivan deserves some credit, the upsurge is also the result of "win now" trades and young depth.
While they made some minor moves in 2016 and 2017, it was the deals of the summer of 2015 that made the difference.