I thought the same thing upon seeing that Bill, and when thinking of who would be a better choice, Walker listed the same three names I had in mind: "Mean Joe" Greene, Jack Lambert, and Franco Harris.
Greene was the Chuck Noll's first ever draft pick and the first big piece of the Steelers' dynasty. Franco meanwhile probably lost points because he finished his career as a Seahawk.
Bradshaw career statistics are mediocre and he was injured quite a bit in his career. But he got it done in the big games, could scramble when he needed to, and had a hell of an arm. He got the votes from the fans because he's the easy choice and is seen by many to be the face of that 70s dynasty.
^
Personally, I think THAT was the face of the dynasty. I'd have to call Lambert the greatest Steeler ever, because he may very well be the best to ever play his position.