 Solution

Increasing the dark energy density makes dark-energy domination begin earlier. The larger Hubble parameter strengthens the $2H{\dot{\Delta }}_m$ friction term while the clustering source $4\pi G{\bar{\rho }}_m{\Delta }_m$ continues to dilute, so less large-scale structure of the universe can grow from a fixed primordial amplitude.

Deep in cosmological-constant domination, $H\simeq H_{\Lambda }$ is constant and ${\bar{\rho }}_m$ is negligible. The growth equation reduces toand henceThe surviving mode is constant: matter growth freezes.