Interestingly, the same pattern has held in California, one of the largest economies in the world in its own right. It's the real reason CA has become so blue: Republicans cut services and run up huge debts, usually coupled by corruption and environmental degradation. Democrats govern more holistically.

Nationally, the difference is probably because Democrats’ policies include investments in the society and everyone. Republican trickle-down idea has been shown not to work over and over again. If you think about it, having just a very few people with all the money (and power) is a kind of economic choke point. The richest do create jobs, but those will never circulate money in the economy like millions upon millions of people being job creators and also getting the investments they need to succeed, which is what Democrats try to do. Republicans characterize the investments that everyone needs in their economic productivity, like education, healthcare, childcare, small business loans, like they’re handouts, even as the richest benefit disproportionately from public investments and get their taxes cut so they never pay the public back (roads, airports, ports, transportation infrastructure, first world markets, the healthcare system, education of their workers and the educational system, the monetary system, the judicial system, public safety, public works, the power system, the military, etc etc etc.)

Before Republican supply-side took hold, far more of the economy was driven by way more middle-class small businesses and job creators. There was a time when this broad-based economy was supported by both administrations, such as under the (Republican) Eisenhower administration.

But if the richest get to keep a disproportionate share of wealth rather than having to pay back to the public the massive/historic public investments that made it possible for them to succeed (public investments have been decimated since the Reagan years because of the ideology), then the power the richest derive from this concentration of wealth then works against democracy. That’s what “plutocracy” is, government of, by, and for the few super-rich, rather than government of, by, and for the people. ***

Check out this Pew Research article on income inequality since 1970 — scroll down and look at the charts showing what’s happened to the wealth in our society: the richest basically took all the money and income from the middle class and poor. (Where is Ross Perot with his charts and graphs when you need him?) That means millions fewer job creators -- and spenders. A top-heavy plutocratic situation like Republicans keep trying to install creates a very fragile economy, too.
https://www.pewsocialtrends.org/2020/01/09/trends-in-income-and-wealth-…

This has never been capitalism versus communism, as the right likes to portray it, but about plutocracy (Republicans) versus democracy (Democrats). It has been for 50 years. It's what the Supreme Court conservative dominance has been about, too.