Very important to understand that gravitational mass is not the same as inertial mass. A small amount of inertial mass could generate large gravity. But reverse is not true. The structural arrangements in a mass specially black holes could generate enormous gravity without having sufficient mass. Concept of singularity is imaginary and baseless. Application and generation of gravity is dependent upon permeability of matter to basic cosmic flow of elementary particle, and divergence imparted to its flow by matter.

The simplified principles of universe function based upon Super Unified Theory by Dr Abhijit Thakur have all the answers posed by dark matter fundamental physics of cosmology.
A physicist would never reach the target of universe functioning because of their approach of hitting extremely out of target.
Understanding matter and energy in universe needs reorientation. The energy and matter we see and perceive in universe is very very small part of energy & mass of universe. True energy and mass of universe is enormous, billions of times more than observed mass.
Second important reorientation in concept is inequality of gravitational mass and inertial mass. This simple but not understood concept is basis of enormous gravity of black hole. It is beyond any doubt that there is no singularity in a black hole. The most of the mass or matter of black hole is lost along relativistic jets. And a vacuum filled black hole generates enormous gravity due to its structural properties described in super unified theory.
This enormous gravity sans mass or matter is falsely interpreted as DARk MATtEr in centre of Milky Way.
I have answers for all queries of universe and cosmology. Gradually it will be exposed as super unified theory becomes popular.(Thakur A. Super Unified Theory, Createspace Edi. 2016 )