This wasn't a failure of enforcing a contract. It was a failure of employees of Credit Suisse to take action after (correctly) identifying risks in their Arche

This wasn't a failure of enforcing a contract. It was a failure of employees of Credit Suisse to take action after (correctly) identifying risks in their Archegos deal. Multiple departments at CS saw the risk. They failed to take action because they didn't want to loose a client who was paying them money.