While they may not have been aware of all the risks, they were certainly aware of most of them.
I'd be interested to know what they think the AFL could have done differently to protect them from these injuries.
As Ken mentioned, some of the other Leagues were far more brutal than the AFL/VFL ever were. Should those Leagues now be basically sued into oblivion? There is a point where you have to accept the consequences of your own choices. A point where someone says, you knew there risks involved when you started. Will future AFL/Any League players be forced to sign a consent form/waiver, attesting to the fact, that they are aware of the risks and accept responsibility for them, every single game, before taking to the field?
The inevitable long term upshot, if this class action has any sort of success, is the end of football as we know it. There is a gladiatorial aspect to the game. Remove that, and the popularity will wane. You can't keep sanitizing a product, and expect people to accept it is the same product they have always loved.