See the link for a lot of history that happened before Knute Rockne spent a summer at Cedar Point. As is noted indirectly in the following message news about football innovations spread slowly, there was no internet. Even up into the 50s a common way of learning about a school that pioneered something groundbreaking (like the Oklahoma offense and defense) was to hire someone from the staff or a former player. ND's role in using the pass was a function of the Army game being of so much interest it got national coverage. BTW has noticed that when it comes to older sports history something interesting but not necessarily accurate that gets written up often gets picked up without fact checking and becomes part of "history."
A historical perspective on the origins of the passing game: http://www.smithsonianmag.com/history/the-early-history-of-footballs-forward-pass-78015237/