300 Foxes and a Donkey's Jawbone
The first axiom of popular science (SciPop) is There's a causal relationship between space-time and gravity. It's Newton's law of universal gravitation. Dark matter is a major deity in the atheist pantheon assigned to defend this axiom.
Before you choke with indignation about our stupidity because we're apparently unaware that there are photographs of a black hole, let's bring up the issue of epistemology. What is knowledge?
Dark matter doesn't exist anywhere outside the popular science paradigm (SciPop). It's not a fact. Its existence is desired because the alternative is a firmament on the edge of space which is incompatible with the SciPop narrative.