Why? Until you study how plasma behaves in a universe 99.9% plasma and stop treating it as neutral dust and gas, you won’t understand.
Until you come to accept that states of matter behave differently, it’s pointless. Until you come to accept that gravitational theory only applies to solids, liquids and gasses; .1% of the universe, planetary systems; you’ll continue to find your accepted theories falsified with every observation. Gravity is only the dominating force in neutral matter, which comprises .1% of the universe. But at the time when it was proposed, people believed that the universe was 99% neutral matter and 1% plasma. With enlightenment has come the knowledge that it is just the opposite, yet they continue to apply the wrong theory to the wrong state of matter as the dominating force. And hence they are surprised by the observations every single time they look into the telescope.
No, there is nothing wrong with gravitational theory. It does not need modified, it simply need to be confined to the states of matter it is applicable to. And hence the second one leaves the confines of the solar system, what was just shown to be 99% correct, suddenly needs 96% ad-hoc Fairie Dust added to make it even seem to reflect a semblance of reality.
Peratt, a world renowned plasma physicist needs no dark matter to explain galaxy rotation or formation. Just plasma physics in a universe 99.9% plasma.
http://plasmauniverse.info/downloadsCosmo/Peratt86TPS-II.pdf
And the Nobel prize plasma physicist Hannes Alfven tried to tell them over 40 years ago they were headed down the wrong path.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870005703.pdf
As he rightly stated. Cosmology can no longer be left in the hands of those who get their knowledge from textbooks which have been shown by laboratory experiments to be wrong, and have never set foot in a plasma laboratory.
One would think in a universe 99.9% plasma, astronomers and cosmologists might want to study plasma physics, but it appears they still haven’t got a clue.