It's true there are far more failed head coaches than successful ones. Though this particular scenario I'd argue is contradictory logic, or atleast circular.
The Steelers can't fire Tomlin unless they "have a guy you really think can make a difference", but they've shown no indication of being willing to explore finding said candidate because they already have one in their opinion.
So what's the criteria for a difference making head coach for this team then? When does Tomlin fail to meet that criteria? Another year without a championship? Two? Three? After Ben retires? Another decade like the 80s teams? One has to exist no?
They've had three coaches since the 70s, and using that logic their coaching hiring process has either successfully chosen sufficient difference makers each of the past three times, or there's some aspect of how the owners structure and run the team separate from the coaching that keeps them consistently successful. If it's the former, their track record indicates they'd successfully find the next difference maker, or at least leave more than sufficient doubt they'd "risk setting their organization on fire". If it's the later, the resume of the head coach or his potential replacement is irrelevant.
Either way, using that logic there's little risk in at the very least exploring other potential options, yet because of Tomlin's resume (which again he himself did not have upon his hiring) they refuse to do so. So is the head coaching position of the Steelers really a retirement gig? A blank check in a sense?
Maybe they win next year and this discussion is proven moot, but my question is from now until his theoretical retirement, does a criteria exist for this team's head coaching position that he can fail to meet?
If so, what is it?
If not, what purpose does his resume they defend him with actually serve?