You have to ask which way the causality runs. Is SMC government good because SMC is full of rich people, or is SMC full of rich people because it has good government, which attracts rich people to move there? Or is it both working in a virtuous cycle?
it probably is a bit of a virtuous cycle but i'd argue that richer people generally demand more accountability and have more power to enact change from their local government than poor people - whether this is due to richer people being better educated, or having more free time to think about local politics, or a sense of entitlement for getting more out of society etc... i think they all play a part in being engaged in local politics and having agency to effect change.
Well, the US are one of the richest countries in the world - so it's a bit mind-boggling that most cities (apparently) have problems providing basic services...