Auditioned six times for the role of Annette in La Fièvre du samedi soir (1977) - three times for original director John G. Avildsen then, after he was fired, three more times for replacement director John Badham - before she got the role.
I don't think you can ever perceive this sort of lightning in a bottle, I think they were hoping it would do at least well enough to make it's money back. Then, suddenly, it became so popular it took on a whole other life.