The stars and clouds of the Milky Way do not orbit the central black hole. They orbit the center of mass of the galaxy. Even if the black hole were not there at all, that spot is still the center of mass, the point where the entire mass of everything in the galaxy appears to be concentrated to a test mass outside.
The black hole probably appeared after the galaxy formed, not before, and it probably formed gradually as material slowly accumulated there. And if that central black hole were to magically disappear, the general architecture of the galaxy, what astronomers call a Grand Design Spiral, would not change in the slightest.
I stress this point because, as I point out in my lead post in my original thread, black holes are not apocalyptic gulpers of space-time, they are just ordinary gravitational attractors. The million solar mass black hole at the Milky Way’s heart is no more powerful an attractor than a globular cluster containing a million solar mass stars. The only difference is that the central black hole is a very compact object, only several light-hours in size, and if you get too close to it you’re toast.
A globular cluster with a million suns is about a hundred light years across. You could easily fly a starship right through the middle of one and emerge unscathed out the other side. But from a distance, its gravitational effects on its surroundings are identical to that of the black hole. It’s gravitational force at any given distance is the same as the black hole’s.
Incidentally, there are several hundred globular clusters orbiting the center of mass of the Milky Way (in fact, most galaxies have their own little cloud of GC’s buzzing atround them) in highly elliptical orbits.