The NFL case was slightly different because there was a misplaced belief that the collisions weren't regular enough and that the protective gear was sufficient. The CTE findings there had more to do with hidden symptoms leading to mental illness among other things. Despite what the movie Concussion with Will Smith said, the idea that blunt force impact could have negative cognitive effects wasn't new to anyone in the sports world. Pugilistica Dementia was a group of symptoms classified as associated with boxing in particular. It's since been reclassified as a sub-category of CTE now that we know more than getting repeatedly punched in the face can cause it. I lived through the 90s and even trained. Everyone knew what being punch drunk meant.