They didn’t know just how evil and partisan their own base was until Trump demonstrated it for them. They spent years using conservative media/echo chamber sources to make their base paranoid, outraged, and hyper-partisan, but even then, they still used dog whistles. They didn’t think they could just come out and say the most horrible shit imaginable and get away with it.
Remember when Trump was first a candidate, and most of the republicans talked about what a dangerous kook he was? Because he was doing all the stuff they were doing, except he said the quiet part out loud. He didn’t used dog whistles. He just came out and said and acted in the worst possible fucking way someone could act, and embraced the things they only hinted at. And they thought “well, fuck, this is going to cause a huge backlash against us since they’re just going to lay out bare how shitty a huge portion of our base is”, and hence, the NeverTrump movement.
And it turns out they underestimated their own base. They were horrible human beings beyond what they even cynically imagined. There were fewer people of principle who would reject what Trump was than they ever imagined. They were more cult-like, more “I will support my own tribe against the enemy tribes no matter what they do or how much it conflicts with any principles I have” than they ever imagined.
They were terrified that Trump would be the undoing of their entire dog whistle hint hint outrage mongering campaign of the last 20-30 years, but it turns out that he was the one that proved republicans were worse than even the most cynical republican politician who was pandering hatred to them ever thought.
It turns out there was no risk. 40% of Americans are on board with literally anything any republican wants to do, no matter how blatantly evil. And it also, just as importantly, turns out that the other 60% are fucking useless at stopping it. They blatantly broke all sorts of laws and norms, and suffered no significant pushback. They went into an alternate reality of conspiracy theories and just flat out denying reality, and there was no significant pushback. It got rolled up into the norms. News media just started talking as though living in a fantasy world where you draw hurricanes on maps in sharpie is just a normal part of politics now. They launched a deliberately planned violent insurrection that attempted a coup on the US government and suffered no consequences. Slaps on the wrists for the people who actually stormed the capital, and nothing for the people who planned and encouraged and facilitated it. Their official party line is The Big Lie, an ongoing, unambiguous attempt to break the democratic processes in the US… and no one is doing shit about it.
There are no consequences. They have no scruples, no principles, absolutely no moral or ethical or principled base to keep them in check. The institutions of justice in the US have completely failed to enforce either the law or the institutional norms of democracies. The opposition party is so wildly incompetent at stopping them that I can’t even comprehend it. They are living The Big Lie, they are in the process of a coup, and there have never been nor will ever be consequences. They win, because there is no goodness or decency inside them to stop them from using any evil tactic available to them, and because no one is at all willing to stop them. It’s already over.