Which would seem to have some impact on future ‘dark matter’ theories in that, maybe they’re not necessary to invoke. If these galaxies were ‘hidden’ than so were their gravitational effects.
Nope. Dark matter is manifest in and around individual galaxies. It has no intergalactic effect.
In 20 years, they will find 20 trillion other universes. Then all scientists realize that this is all useless... and commit suicide.