We don't measure dark matter, we measure some anomaly and then we say "it must've been dark matter".
It's not crazy different from saying the same about that poltergeist.
It's not crazy different from saying the same about that poltergeist.
We know of particles which behave the same way. Neutrinos for example.
We are not measuring dark matter, we are measuring something that is not what we expect and we decided it's dark matter.