What crucial observation from the Bullet Cluster provided evidence regarding the interaction nature of dark matter?

Answer

The majority of the mass passed right through the collision without slowing down, separating cleanly from the gas

When colliding galaxy clusters were observed, the visible matter (gas) slowed down due to interaction, but the gravitational mass component passed straight through, indicating dark matter is collisionless on that scale.

What crucial observation from the Bullet Cluster provided evidence regarding the interaction nature of dark matter?
universematterdark matterdark energycomponent