The two parties are not mirror images of each other.
The extremes are in control of the GOP.
The extremes are isolated by the majority of Democrats.
The GOP was so good at gerrymandering after the 2012 election that they destroyed their party. Most incumbent GOP Representatives calculate there is minimal threat of losing to the Democrat in a general election. The risk is being "primaried." Trump openly condemns Republicans if they aren't totally on board with him. He calls them RINOs: Republicans in Name Only. GOP Representatives hear the threat and toe the line.
That is why 147 Republican U.S. Representatives voted to disallow electoral votes for Joe Biden in the aftermath of the January 6 riot. It was why nearly all GOP Representatives voted to choose Jim Jordan to be their Speaker. Better to choose a "legislative terrorist" who would shut down the government, defy House subpoenas, and overturn an election rather than choose a bipartisan Speaker. The House GOP is led by its "Freedom Caucus," which is angry, militant, and extreme -- and proud of being so. To be any less is to be a RINO.
Here is how a typical Trump fundraising letter begins, opening with an attack on RINOs, not Democrats:
U.S. Rep. Rashida Tlaib, who represents a District in Michigan with a high number of Muslim residents, says things which are shocking, extreme, and objectively dishonest. She defended the Hamas attack on October 7, calling it fair payback; she immediately blamed the hospital explosion on Israel; and now that further investigation appears to show conclusively that this was not an Israeli missile but rather a misfire from Hamas, she is sticking with her blame of Israel. It is inaccurate. It is morally wrong. It is dangerous. She is a Democrat.
The difference between Democrats and Republicans in this moment is that Rashida Tlaib is not a candidate for Speaker getting 200 Democratic votes. An overwhelming majority of Democrats condemn and shun her. Republican officeholders and Fox News use Tlaib as the straw man spokesperson for Democrats, but that is dishonest. She is an outlier. So is Bernie Sanders.
To the disappointment of many Democrats, the party rejected Bernie-Sanders-style economic populism and Rashida-Tlaib-style overt support for Palestinians. Instead Democrats chose as a presidential candidate a centrist moderate, Joe Biden. A Democratic House majority under Nancy Pelosi passed bipartisan legislation on infrastructure, energy, and guns that had widespread popularity. Biden supported and signed them. Biden's positions on Ukraine and Israel are mainstream and have bi-partisan support. Democrats have partisans who push the envelope for change, but they are absorbed into a broader coalition that is incremental, not radical.
Republicans have caved in to their most Trump-ish MAGA militants. Trump insists on it. Democrats instead chose centrist moderation. The parties are not mirror images of one another
Absolutely right. And it's not mere moderation that triumphs; it's moderation coupled with pragmatism, institutionalism, and persistence. "Moderate" Democrats have achieved some very progressive goals, and developed further goals for the future.