Aspexia Rugatonn is permitting herself to stay awake too long in her vast bed of Asmodean grandeur, thinking about how much she doesn't like all this, instead of just ordering her own mind sharply to behave. She also has an instinct that it will be dangerous to order her own mind to stop thinking about this.
She really doesn't like the moratorium on Maledictions.
Aspexia sees the rationalization. She sees the excuse. Pushing Cheliax in the direction of some cheap Goodness will assist in the spread of Sevar's legend and cult and her eventual ascension. Which, yes, serves Sevar more than Hell, but Sevar no longer lawfully answers to Rugatonn about that; only Dispater can bid her otherwise...
Swearing off Maledictions is undeniably an efficient way of producing a public shift in the perception of Cheliax under the Sevarian Empire. It gets them to maybe consider that Cheliax might be starting over, that Carissa Sevar is on their side, to want that to be true. It lets people hope...
Just like Aspexia Rugatonn is being allowed to hope, herself, that their hope is a lie.