Forty-odd years ago, Reagan defined the Republican coalition as a three legged stool. These legs may not have pointed entirely different directions the way that anarcho-communism, technocratic populism, or global nativism would, but they certainly didn't hold the same centering base principles. Functionally, definitionally opposed and cross-purposed to one another, they all the same began their dysfunctional, disastrous courtship which matured into strong and enduring toxic partnership. In theory, they believed they could advance their common goals by making concessions on the margins to each other in exchange for the strength that numbers provide.
Self-deluded, the right convinced itself that there was actually some fundamental natural alignment between the three rather than a relationship born of political expediency. A world of fiscal cons, social cons, and neocons living in harmony rather than chaos, believing fusionism functioned as symmetry... is madness.
Every honest fiscal con recognizes the financial cost of unjust war, and every honest social con recognizes the immorality of it. Fiscal cons recognize the cost of prohibition, and neocons recognize the types of war social cons would support aren't in the national interest. Social cons can understand that fiscal conservatism is rooted in the freedom inherent in self ownership and individualism, rather than adherence to conforming to a higher traditionalist power, and neocons aren't naive enough to recognize that the utter incompatibility of thrift and war makes fiscal conservatives at very least a future enemy.
The cold war may have provided more overlap than one would expect, especially given how readily humans define their own beliefs by what they're opposed to, what Dershowitz might phrase “rights from wrongs”. Communism was rightly seen as a threat to financial freedom, religious freedom, and America itself. Inwardly, federalism might have been able to smooth out some of the frayed edges and provided an out for the seeming contradictions. But it couldn't last, and the coalition had been dying since the lifting of the iron curtain. Determining the cause or time of death might be tricky and it's more complicated than just “Trump”, but recognizing it's a corpse shouldn't require a biologist.
The GOP has long jettisoned any sense of fiscal restraint, and opposing gargantuan Democrat budgets doesn't count if their alternative is essentially gargantuan Democrat budgets from a year or two ago. Their “moral majority” overwhelmingly turned out for a man with the character of Donald Trump. Neocons may still hold the levers of power at the top, but at the grassroots level the average Republican has become more skeptical of war and pro-war propaganda than the average Democrat.
So what legs have replaced Reagan's tripod? There's plenty of words that come to mind such as nativism, nationalism, populism, etc. which all may play some role. But the only visible connecting tissue I see in today's Republican party is “owning the libs”. There seemingly isn't an important, set, coherent philosophical difference defining the GOP, and all that's left is cultural identity and hating the other guys more than they hate one another. Defining oneself by opposition allows your opposition to set the terms and what today's GOP needs is an actual soul. What defines them now is relatively rudderless anger and a (correct) understanding that the modern left has lost it's marbles.