In Achebe’s Things Fall Apart, why is Okonkwo’s punishment for killing Ezeudu’s son relatively lenient?

Ezeudu’s son did not belong to the same clan as Okonkwo.
Okonkwo belonged to a higher social caste than Ezeudu’s son.
It was considered a “feminine” crime because it was unintentional.
Manslaughter was a “masculine” crime so the punishment was less severe.