The arrogance of the NFL was disgusting
Didn't even need science to tell you what common sense does. Bang your head repeatedly over time and bad things will heppen.
This was a little more than common sense. You can bang your head against the wall and fine. It takes a doctor and/or a scientist to know about the fluid surrounding your head, and how your brain isn't really connected to your body. The issue with concussions is that you can feel fully recovered, but have long lasting effects from prolonged abuse.
It's like how you can feel fine after cigarettes, but not know that lifelong abuse causes serious health risks. You'd only know if you ran the studies, or trusted the right people who did the studies.