The Penguins are a phenomenal example of what happens when a loaded roster has a bad coach. So are Boudreau teams, Bruce being terrible in a playoff series.
You ignored your task, so here it is again: Name the bad coaches who have won without a generational talent.
They were not a loaded roster.
When Sullivan went to the playoffs, they replaced eight of twelve forwards and three defensemen on the previous year's playoff team. So it wasn't just a new coach, it was an entirely new team, including a hot young goalie.
The year before they won the Cup, they had Crosby, Malkin, Hornqvist, Kunitz, Perron, B Sutter at forward.
Their depth: Comeau, LaPierre, Winnik, Spaling, Downie, Bennett/Wilson
Letang on defense. Who got injured.
Leaving Martin, Cole, Lovejoy, Scuderi, Chorney and Dumoulin (who had spent the year in the AHL)
That summer, they got Letang back and added: Kessel, Matt Cullen, Nick Bonino, Olli Maatta, Eric Fehr
Then after Sullivan took over, before the TDL, Tevor Daley, Carl Hagelin, Conor Sheary, Brian Rust, Tom Kuhnhackl, Justin Schultz and Matt Murray.
So they replaced Sutter and Perron with Kessel and Bonino in their top six and Hagelin pushed Kunitz down.
Replaced the entire bottom six from the previous year.
On defense, only Lovejoy, Cole and Dumoulin returned from the previous year's playoff squad.