No team had ever won the Superbowl when their running back led the league in rushing yards in a season until Emmitt did it three times.
The notion that what happened in the past is indicative of what will happen in the future is pretty much made moot as records continue to be broken.
Well yeah. I'm not saying it's impossible to win it all with the most passing yards. But there are reasons that it's unlikely that you would and evidence that supports that.
If you're winning games by passing the ball a lot, you're probably a pretty unbalanced offense that can be defeated by a tough playoff defense, winter elements, or a combination of both.
Best example-- Drew Brees. Since he joined the Saints in 2006...
1. He's been the leagues leading passer 4 out of 7 years, eclipsing the 5,000 yd mark 3 times.
*(2012, 2008) 2 of the times he's surpassed 5,000 yds, the Saints failed to make the playoffs.
*The other time he passed for over 5K, he was defeated at Candlestick by the 9ers, a tough defense.
*The first time he finished 1st overall in passing yards, he was undone in Chicago in the NFCCG-- because of a strong defense and the elements. It's also important to note that even though he led the league in passing this year, he only passed for 4,400 yards.
2. Of the remaining 3 seasons when he wasn't the top overall passer, he finished within the top 3 for yardage in 2 separate years.
*In 2010, he finished 3rd in passing with 4,600 yards. He was undone by the elements and a stingy defense in Seattle.
*In 2007, he finished 2nd overall in yardage, did not make playoffs/finished 3rd in NFCS.
3. The only year he finished outside of the top 5 in passing yards, the Saints won a super bowl.
Again, it's not impossible to win a super bowl while having the most passing yards, but usually it's pretty tough because it means you were probably relying on amassing yards via the passing game too much because of lack of balance/ lack of defense/ lack of takeways/ lack of good field position, etc.
And it's not just Brees. The last few great passing yardage displays in the regular season usually failed in the pressure of the playoffs (Think Brady in 07, Rodgers in '11).