It's not the galaxy's rotational axis, exactly; it's the rotational axis of the (currently present) infalling gas. That may tend to align with the galaxy's axi

It's not the galaxy's rotational axis, exactly; it's the rotational axis of the (currently present) infalling gas. That may tend to align with the galaxy's axis, but there's probably a lot of variation. (When a star is getting sucked in, it's going to contribute pretty heavily, and star orbits in the core are not at all correlated with the axis of rotation of the disk.) All this is my understanding only. I'm not a working physicist.