Long answer is long but here's a way to think about it that is physically accurate and not oversimplified as far as I know (I took general relativity 15 years ago so things get fuzzy and I could be forgetting a relevant detail or two)
A dark energy dominated (ie accelerating expansion) universe will have negatively curved spacetime at very large scales. The gravitational effect of regular mass (baryonic and dark both) is to generate local positive curvature of spacetime, which causes the geodesics of nearby objects to bend toward the mass aka falling inward. If you have a large amount of mass sprinkled throughout the universe, the positive curvature generated by that mass will partially offset the negative curvature effect caused by dark energy, slowing expansion.
everythingist t1_jak455w wrote
Reply to Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47
Long answer is long but here's a way to think about it that is physically accurate and not oversimplified as far as I know (I took general relativity 15 years ago so things get fuzzy and I could be forgetting a relevant detail or two)
A dark energy dominated (ie accelerating expansion) universe will have negatively curved spacetime at very large scales. The gravitational effect of regular mass (baryonic and dark both) is to generate local positive curvature of spacetime, which causes the geodesics of nearby objects to bend toward the mass aka falling inward. If you have a large amount of mass sprinkled throughout the universe, the positive curvature generated by that mass will partially offset the negative curvature effect caused by dark energy, slowing expansion.