Wikipedia: The supermassive black hole lurking at the heart of the Milky Way – Sagittarius A*, or Sgr A* for short – contains about 4.3 million solar masses, and, as it turns out, nearly all of the mass at the very center of the galaxy.
Suggestion: Only smaller Herbig Haro Black Hole systems are ruling the inner structure of the Milky Way galaxy by forming disc planetary related stars and even dead stars.
During new Herbig Haro HH star formation, stars are growing at a maximum mass before they seem to eject new "ORPHAN STARS" as a lonely stars.
The mass of HH stars becomes too large for a stable balance, ( "local vacuum polarization oscillation " between the dual mother Herbig Haro Black Holes ( SABHs: Stellar Anchor Black Holes)
However according to Q-FFF Theory, there should also be so called "Galaxy Anchor Black Holes"(GABHs), created out of the black hole spitting and splitting Big Bang.
see also: What is Wrong with Current Physics,to Explain Ball Lightning.
see below: