Gosh. I seem to remember gravity having the same sort of behavior.
The presence of dark matter is inferred by its presumed gravitational interaction with visible matter.
One of the reasons for the study was that gravity can’t account for what is being observed. I’m no expert, but that’s what I’ve read.
Gravity does, but there is insufficient observable matter to account for all of the gravity necessary to explain the structures we see. Therefore some non-observable matter must account for the extra gravity. Hence, dark matter.