What happened to conservatism is the Civil Rights Act and the resulting realignment.
When Southern Dems were the segregationists, they were reactionary on race but they were New Dealers; believed in government regulation; believed in community; believed in caring for fellow white people. So they were never conservative. Just reactionary on a few issues.
But after the realignment, which really wasn't complete until the 1990s, the racism and the plutocracy was on the same side. There was not too much left that could be the basis for any sort of empathy. It was toxic individualism, atomization, tax cuts, exclusion, and drained pool politics.
And when the educated classes started swinging more to the liberals in the 1990s, it created the perfect storm for Gingrich.
Note also in the 1990s, there was an influx of erstwhile Marxist academics who found themselves newly relevant to American politics. Their engagement with liberalism, as opposed to the previous disparagement of it, also helped (I would suspect; I don't know) with the educational shift to the Dems.
Thus by 2000 did the GOP assemble a coalition of uncaring, racist ignorance. What we've seen this century is the fallout. Nothing good ever comes from letting in the inmates run the asylum. Like, even if you think they are right on the big issues, they are still fucking lunatics