And with the NFL in particular, the powers that be in the league for 50+ years conspired with specifically selected doctors to manipulate the players into believing the sport was safe. They lied, cheated, and hid evidence to the contrary to fuel their own success. In fact, they continue to do so and refuse to acknowledge the facts you just laid out.
In other words, players thought that playing in the NFL was safe and they couldn't get hurt, all because it was a conspiracy. They didn't realize that hard physical contact could cause injuries....gotcha.