Game theory tells us that when there are two strategy options, like run and pass, the expected payoffs for both options should be equal. You really don't need game theory to intuitively understand this. If one option yields a better payoff, then it should be chosen until the opponent responds with a strategy change of his own. Eventually, as the opponent responds, the payoffs for the two options equalize. The point at which the strategy mix equalizes payoffs is known as the minimax, or sometimes called the Nash equilibrium. The resulting strategy mix, or run-pass balance in this case, produces the best overall, long-run payoff.
When there are two strategy options and one of them yields a much higher payoff, it tells us two things. In this case, passing is more lucrative than running on 1st down, and this tells us: 1) offenses should be passing more often, and 2) for now, defenses should continue to be more biased toward stopping the run.
I was screaming about this during last year's SEC Championship game against Alabama. The Gators insisted on running on first down with Demps, mostly, for three quarters, until opening up the pass and getting most of their offensive success in the fourth quarter. Notice, this is NOT about running, even if it doesn't work, in order to pass later. It is saying that teams are running well over the amount needed to effectively "set-up" the defense.
You'll also notice, further into the piece, that more red-zone passing is needed.