That added to it, but only a small part. The NFL became a pass happy league when Walsh brought the west coast offense to the NFL. The teams that have won the super bowl due a strong run game can probably be counted on a single hand since Walsh. I can name the Bears and Ravens from 2000, but they won mostly off of defense. Point is Walsh changed the NFL and how people drafted. Johnson and Belichick followed suit and everyone has tried to copy since.That is all due to the rule changes occurring in the late 70s and the subsequent adaptation and gradual exploitation of new opportunities.
No longer could you touch a receiver five yards past the LOS. Before this rule, receivers were mugged All over the field prior to the QB throwing the ball.
Extended arms and open hands during pass blocking. Effectively legalized holding and extended the range and effectness of the OL. Much more time in the pocket.
You change just these two rules back and the NFL is a different league overnight.