The Republican Party exists primarily to enable rich people to get richer. Its most powerful tool for drawing public support to this niche cause is racism. Indeed, research shows it.
In the American system, money can directly purchase political power. Wealthy people and business interests have used money to purchase an entire political party. (And much of the other party, too, but at least that’s a mixed bag.) The entities who fund the Republican Party do so as an investment. And that investment pays off in the form of tax cuts and deregulation. You’ll notice that tax cuts are the only thing this inept Republican Congress actually managed to achieve so far.
Because “cut taxes on multimillionaires” is not a strong “populist” message, the Republican Party uses religion and patriotic flag-waving and culture wars to attract votes, out of necessity. But what works better than anything for this purpose? Racism. It is well understood and widely accepted that the shift among Southern voters from the Democratic to Republican Party occurred largely as a result of direct racist appeals by the Republicans, spurred by the civil rights movement. For the Republicans, civil rights were simply an opportunity to capture racist voters. And it worked.