As someone who's proved the fallacy of hypothetical 'dark matter'
'Dark matter' is Provably Wrong. If one thinks about it almost all galaxies behave rotationally differently than one would expect from standard gravity. In the Solar system Mercury orbits every 88 days, while the outer planets take hundreds of Earth years. That entails very different Rotations...
forums.space.com
there must be preexisting gravity/curvature, possibly from some other source, even possibly extra-universal ones, since i have dovetailed Godel's proof the Universe can not be absolutely closed.
So it is interesting to speculate the super massive black holes may be a mix of pure matterless gravity (mass) as well as some actual matter falling into a preexisting gravity trap.
That could help explain how they formed so early in the Universe.
(off the wall thought)
Maybe the event horizon's size is a function of the quantity of matter falling into it?