I think dark matter is likely what our space time exploded into with the Big Bang, explosions are not like inflating balloons they are scatter shots.
like the other poster said , it likely has no effect on our space time, it’s likely the culprits for spooky action at a distance as it’s mass and energy out side our space time or it has no mass and energy yet it has gravity where our gravity can over lap and motion can spot us feeling gravity maybe dark matters gravity is different. It’s a negative so our universe gravity is attracted to it like positive and negative Charges are in our space time.
a dark matter void with a negative gravity charge could explain our universes expansion.
also dark matter could be a result of matter hitting the singularity at the centre of a black hole.
Energy gets converted to the event horizon and the singularity is a gate to the dark matters native space time. It could be Following dark matter space times gravity into our space time sucking In our matter.