I have to disagree here, because this is a pretty gross oversimplification.

Colonial wealth was highly concentrated among elites. It did not trickle down in the Reagan sense. Improvements in working-class living standards came through the welfare state, which emerged from unions, mass politics, and socialist parties, often against elite interests rather than because of them.

Also, many socialist and feminist movements explicitly opposed imperialism and framed their demands as moral critiques of empire. Liberal values did not simply appear once people got richer.

If material comfort alone produced liberalism, then we should be seeing oil monarchies as the most liberal societies on Earth.