Comment by devmor
16 hours ago
I believe that you have the order of operations misunderstood.
I probably don't know that much more than you about the subject, but from what I understand, the prevailing model suggests that these Halos formed early in the formation of the universe when spacetime had varying "pockets" of density that naturally led to these halos - the formation of the galactic disk therein was actually supported by the halo existing first, because baryonic matter (aka non-dark matter, the stuff that makes up planets, stars, etc) was still too energetic from the formation of the universe to become gravitationally bound to itself.
Does the dark matter not move under the influence of gravity like 'normal' matter?
it does, but it orbits the barycenter (usually the supermassive blackhole of the host galaxy), but since it can pass through itself its orbital energy doesn't decrease from "drag" as it's falling through itself and normal matter
At this point my knowledge probably pales in comparison to skimming some Wikipedia articles, but my understanding is that there is just so much dark matter concentrated in these halos and inter-galactic structures of it that the gravitational effects of baryonic matter are negligible in comparison.
I believe dark matter comprises something like 80-85% of all matter in the universe.