Notre Dame has apparently always used FB "profits" for the general fund. Have read and heard "old timers" (when I was a student in the 60s) talk about how FB money was used to expand "the plant" starting in the 20s. It provided the funding to see ND thru "The Depression." Pretty clearly the Navy kept our ship afloat during WWII but ND also scheduled a lot of "money games" following the same strategy that has been followed from the days that ND burst on the national scene - doubt if anyone has played as many intersectional games from the 20s on.
Remember well the early 60s when the revenue stream was endangered as not wining resulted in less home attendance (we played North Carolina in 1962 to an actual crowd that was only marginally more that the Spring Game now). While the deemphasis cycle receded for awhile with the arrival of Ara, the very first effort to create an endowment (and the library) reached its goal (a near miracle at the time but subsequent Challenge efforts made that amount look paltry in hindsight).
We are still using those profits to fund ND and a glance at the balance sheet makes it hard to imagine how ND would contract to deal with the absence of those funds (a really big hit looking forward a generation).
It is hard to imagine ND without its FB for $ program. Whatever would have happened would have left its leaders in constant fund raising mode just to keep "the lights on." Many small private colleges of similar age have navigated a path to today and probably more have not.