Here is a 3-paragraph summary of the article for mathopen.com:
Astronomers have discovered a fascinating triplet of "ghostly" galaxies that appear to contain little to no dark matter. These unusually dim and diffuse galaxies are thought to have formed after a cosmic collision, a violent event that may have stripped them of the mysterious invisible matter that typically holds galaxies together. Their existence raises important questions about the fundamental nature of dark matter and how galaxies form and evolve over time.
What makes this discovery especially significant is what it reveals about competing scientific theories. Alternative theories of gravity, which attempt to explain galactic behavior without invoking dark matter at all, struggle to account for galaxies that lack it entirely. If gravity simply behaved differently at large scales, there would be no mechanism to strip a galaxy of that effect. The existence of these dark-matter-deficient galaxies therefore deals a serious blow to those alternative frameworks.
At the same time, the discovery offers valuable clues in support of the traditional dark matter model. Under that model, dark matter exists as a real physical substance that can, under extreme circumstances like galactic collisions, be separated from ordinary visible matter. Finding galaxies where this separation appears to have occurred provides rare and compelling observational evidence that dark matter behaves like a true physical ingredient of the universe, one that follows its own rules separate from the stars and gas we can see directly.