Captain William didn't actually hang all those merchants, even though he could have done so, and Perfikot wouldn't have minded.
But after carefully considering the consequences, Captain William chose to only hang them up.
Don't get it wrong, Captain William was not just letting them go, or thinking this was enough.
The reason he didn't order their immediate hanging was because he hoped to better execute Perfikot's orders and implement the will of the Lord of the North exactly where she desired, rather than simply becoming a dirty-handed glove for Perfikot.
In Captain William's view, Perfikot aimed to resolve the resistance to the child labor law and the New Continent merchants wanting to oppose the authority of the Northern Lord.
Rather than simply hoping to kill the merchants who offended her authority, although it is indeed the simplest, most brutal, and direct method.
