You are mixing up dark matter and dark energy. The main effect of dark matter is not universal expansion, it is from both influences of gravity on galaxies and

You are mixing up dark matter and dark energy. The main effect of dark matter is not universal expansion, it is from both influences of gravity on galaxies and theory. See e.g. https://en.wikipedia.org/wiki/Dark_matter#Observational_evidence https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...