It’s actually easy to understand.
If Einstein is correct about curved space/time, then the expansion of our universe (or acceleration of matter in said universe) can be explained by curved space/time boundaries whose shapes become sharper the further the universe expands (thus speeding up matter).
Dark matter need not apply.
Or put another way, the universe isn’t really expanding...it’s just that matter speeds up as it approaches the sharp boundaries of Space/Time.
Amazing. All those brilliant physicists out there, and you’re the only one who can do the math.