Why are people favoring the Steelers when the Cards have pulled off the impossible throught the post season?

I live in Arizona and I joined the bandwagon for the Cardinals after the season ended. I just want to know why the Cards are considered a HUGE underdog when they beat three TOUGH teams in the playoffs? The Carolina game should have been a landslide victory for the Panthers but they flopped big time. The same should be said with Atlanta and especially the Eagles?