According to Q-FFF Theory, The shortage of Dark Matter inside some galaxies seems to be originated by the absence of the original Herbig Haro Dark Matter Black Hole structure, outside the Galaxies of Galaxy Clusters called GABHs (Dual Star/ Galaxy Anchor Black Holes structure. )
However there are still GABHs in the neighborhood of cluster galaxies forming a central polarisation in the Axion vacuum called White Hole.
Just like to central galaxy position (white hole) in each normal galaxy, (below)
Other Dark Matter Stripping of Galaxy clusters.
The Bullet Custer Dark Matter of the smaller cluster is left behind (at the left side) due to the attraction of the larger cluster due to the majority of Dark matter gravity effects on all NON INERTIAL Dark Matter mostly in the form of Black Holes of variable sizes.
The colors: Purple/blue is Dark Matter, yellow and orange is x-ray gas. white are the galaxy centers.
Conclusion: the smaller cluster is stripped from its major dark matter.
It is assumed that the smaller cluster will decelerate by the new central Dark Matter attraction,to join the larger cluster.
purple and is Dark Matter.