I think you need High Social for that to happen. At least that’s what make it work in my playthrough
Dulsen: Tell him that you’re the best person to deal with the abyssal spawn (you had to kill one first), then say that nobody will follow him if he doesn’t lead in battle or that you need full control. Then offer to make him your minister.
Avellyn: Follow her and accept to make a new religion (if it wasn’t made already) or if you already convinced Dulsen, she’ll vote for you anyway.
Sessanah: Offer her independence if you’re crowned.
None of this really changes anything though besides some dialogue and what’s described.