Back when we interviewed Singletary, he'd never even been a coordinator before and didn't have the Xs and Os knowledge to be a HC. It would've been a real stretch to hire a total unknown like him to run a playoff-ready team. By the time the Niners hired him, at least he'd been a DC for a year or two.
And they stunk (stink) so badly, they had little to lose and were probably willing to let him have a year or two of OJT while he figured things out. That wasn't the case with us.
I do love how some people act like being a drill sergeant is all that matters in coaching. The truth is, plenty of "tough guy" head coaches have flamed out, just like every other style.