I thought the republicans are at the top and bottom of the wealth scale and the democrats are in the middle

Republicans are at the top and good at messaging to the bottom (but they rarely actually help the bottom).

Democrats are just bad all around, bad at messaging and bad at achieving things, but at least they mostly don't make things worse, and people with enough time invested in understanding politics (a minority of people) see that. When things do get worse and Democrats are in charge, Republican messaging is effective at convincing people it's the Democrats' fault (which it kinda is because they did nothing to stop it, and kinda isn't because they did nothing to cause it, and in any case the Republicans are even worse but good at saying they're not).