They were?
In the seven years prior to Cowher's arrival in 1992, the Steelers went 7-9, 6-10, 8-7 (strike year), 5-11, 9-7, 9-7 and 7-9. Mediocrity. There's a reason you don't remember the Bills playing the Steelers in the playoffs during our little run until Cowher got to Pittsburgh: the Steelers weren't IN the playoffs for seven years in a row.
The year before Cowher got there, Neil O'Donnell and Bubby Brister were throwing to Dwight Stone and Louis Lipps. (They did have a young Eric Green and a young Barry Foster.) They had a few kids on defense -- Rod Woodson, Carnell Lake, Greg Lloyd -- but none of them, save perhaps Woodson, had become what they would become under Cowher.
When Cowher got there in 1992, the Steelers drafted Leon Searcy in the first round and Levon Kirkland in the second. That year, they started 10-3 (after not having won 10 games in any of the previous seven years, mind you), went 11-5, won the division and made the playoffs.
His job was NOT to build on what was there. His job was to take a once-proud, then-stagnant franchise and breathe new life into it. That he did. Almost immediately, I might add.