The Republican Party's economic/tax policies have reached a point where the number of people who actually benefit from them is incredibly small.
Unless you are in the top 1% of incomes (greater than $434,000 in 2018) and you make most of that income from dividends and capital gains as a business owner, you don't benefit from GOP economic policies.
Johnson County's median household income is $73,733. Such a household would indisputably be better off under Democratic policies.
But either way, nobody votes purely out of economic interests.
Pretty much this. Also given SALT deductions getting capped many middle-class people in high tax states are paying more than they have before in taxes. There's a reason why wealthy districts in New Jersey and New York voted for Democratic candidates