As expected, Itsuki is the controlling type. That Rio so easily complied suggested trauma.
He likely doesn't even want a divorce. For him, she needs to be punished, not to be set free. People were too blinded by the revenge game to see that someone who could pull this after feigning calm as long as he did had to have issues. Nobody's perfect, and if he was, why would Rio cheat with that clown? Her standards would be too high.
Regardless, Rio deserves no sympathy from me. Itsuki is one thing, but Mahoro deserved none of what Rio did. Now Rei, holy shit this guy is the worst.