mammon being the main sibling who raised satan.
satan has just spawned into existence, everyone's still grieving. lucifer has fully immersed himself in his work. levi is in self isolation under the sea. asmo is indulging in his sin to cope. beel and belph are inconsolable.
mammon is hurting too but he hates sitting around moping. so who better to look after a tiny ball of rage.
he has the most amount of patience and doesn't lash out when things get physical.
not the best at raising a kid but he’s trying.
(( asmo eventually comes around to help too once he’s confident his hair wont get ripped out.))