If you read this study, it mentions people are prone to affective polarization, that is a state of mind that is in itself extreme and it’s related to people being myopic, that is governed by strong emotions such as panic instead of choosing rationally.
Basically, economic inequality leads to elite polarization (at the congress level) that limits the political agenda to policies that do not benefit the public, so that the public can only vote against its interest. This leads to more economic inequality and so forth. There are more layers to it, such as economic inequality creating elites in the private sector and leaving politics to incompetent people that are manipulated by the business elite. My initial description is somewhat simplistic, but essentially the public is cut off from the elite due to economic inequality, leading to political polarization as the only differentiating factor in policy, so that the public can only vote against its interest.