I'm not sure a country with Jim Crow laws while still having a sizeable minority of black voters was culturally homogenous. Same with an active communist movement alongside an active KKK. South-North and city-rural divides were also clear in the infighting for the New Deal, and the conservative, rural, racist Democrats sabtoaged the full potential of Social Security and the NLRA.
Obama came in with an unprecedented-for-the-modern-era mandate, same for his comfortable majority in both houses, same with his approval. He had political capital to burn. He chose the healthcare plan that favoured insurers the most, the bailout that favoured banks the most, an economic team with many centrists and right-wingers (who prevailed in his administration), an AG from Wall Street proudly unwilling to prosecute anyone for their financial or war crime misdeeds. So he foreclosed the alternative way of changing the political equilibrium - passing popular policies.