The experimental observation did not reveal Dark Matter. Nobody has seen or proven Dark Matter, actually. That’s why it is called Dark Matter. The observation just showed that the math model was flawed, and they invented “Dark Matter” to make up for it.
My personal take is that they will one day add the right correction factor that should have been in the fomulas all the time.
Just like with E=mc² not being completely correct. It’s actually E²=m²c⁴ + p²c². The p²c² is not adding much, but it is still there.