Conservatism after Reagan was just a grift.
Love or hate Reagan, he actually did fight for some of the things he believed in. When the Bushes ascended to power, they saw a rapidly declining voter base and decided, like many GOP sellouts, to cash out while the going was good with the Military Industrial Complex while propping up Reagan's corpse. And while they cashed out, they traded hands with the Democrats until one party rule under them would be established, and then probably join them to milk this country until the last bit of wealth is drained from a dying superpower and then move onto China, which they helped create.
Trump, a man who is essentially a 90's Democrat policy wise and more consistantly socially liberal than any president before him, said "Fight back." The Neocons hated it because the grift was disrupted. The Democrats hated it because their one party rule and grift were disrupted. But the Republican base loved it, because it wasn't just a grift anymore. McCain and Romney were made the biggest examples of this, from becoming GOP frontman and faces of the party, to laughingstocks and reviled.
Trump put it best in the 90's. "The most capable people are not running for office and that is horrible commentary on the country. I see it as someone with my views, which may be right, but a little bit unpopular, may not get elected over someone with no great brain but a big smile."
It was all smiles and empty promises before him, and his entire election was a formal declaration of that by the voter.