It's a serious question about Gruden. I don't know who came up with the name the QB whisperer, but I can't think of any great, or really good QBs, that he developed. I guess he did a decent job with Carr, but he didn't turn Carr into a top 5 or even a top 10 guy.
I'm not being snarky here, I really don't know why Gruden would be called that.
And while passion is a good trait in a head coach and is something that Payton had, Dan Campbell has, and many others. It doesn't always come out as the vivacious personality that Gruden has. Bill Wash was passionate for the game but had no personality. Bill Bellichick is passionate for the game but has no personality. Andy Reid has personality and passion for the game, but he's not pumping people up like Gruden and Kyle Shanahan isn't a high energy guy. And while the Harbaugh brothers are demanding and have passion for the game, neither of them have that high energy personality that Gruden has.
So, there is more than one way to be successful as a head coach in the NFL. And the truth is that Gruden hasn't been very successful since his one Super Bowl win with Tony Dungy's team.