young galaxies start only with Super Nova Dark Matter Black Hole production located in the galaxy Halo bubble and line by line merging into the central giant BH. Second: after merging with other galaxies, the dark matter content suddenly increases.
See: Distant galaxies lack dark matter, study suggests.
Different families of Dark Matter Black Holes.
How does all these black holes keep their mutual distance? exept for the small BH near the central BH and BHs with LIGO ratios?
By hydrogen pushing tails produced by the BH itself via pair and quark production at their horizons, pushing away from the local center of gravity.