NFL has relaxed their weed policy in the last CBA. It is not banned like you say.
"NFL DRUG POLICY
Under the 2020 Collective Bargaining Agreement (CBA), NFL players no longer get tested for THC (the active ingredient in marijuana) in April and August. This means that players can now consume cannabis during the off-season without fear of punishment."
"Players who consume weed during the season can enter a treatment program and avoid suspension.*
https://blackcannabismagazine.com/nfl-weed-policy-can-players-smoke-weed/amp/