What made the Steelers different in the late 1970s from the mid 1970s is that their offense changed when the rules. Changed in 1978 to improve the blocking and put in the illegal contact rule so WR's could get off of the line of scrimmage. In the mid 1970s they were a defensive club that relied on their defense to get them great field position and get them takeaway's. With a power run ball control offense and deep threats in the passing game with John Stallworth and Lynn Swann at WR. When defenses stacked the line of scrimmage to take away the running game. That type of offense was no longer good enough with the new rule changes to open up the passing and running game. Even with the Steel Curtain defense the Steelers had to find more ways to score and score more often as we saw in Super Bowls 13 and 14 against the. Dallas Cowboys and Los Angeles Rams. And Terry Bradshaw emerging as the best QB in the league and best big game QB in the league made the Steelers great on offense as well.