Yes there is something you are missing... that lie does not violate any criminal statute that I know of, therefore there is no crime and no jail for Goodell.
What you do have though might be actionable fraud in a civil case. There is a cause of action for fraudulent concealment that may be brought against the league by players that were 'lied to' by the league and suffered concussions as a result of the lies. Of course these players would have to prove that if they had known about the danger they would not have played the way they played, or played at all.