The second scenario, far less likely than the first but still conceivable considering Trump's past as a New York Democrat and the Conservative apostasy in his campaign, was that Trump would cut centrist deals and govern as a moderate. He might, for instance, win some tax cuts and regulatory reform, but he would trade away the Ryan-McConnell ambition to end government healthcare. This was the scenario conservatives feared most and sometimes it still haunts them.
The third scenario (the one that's actually come to pass), is that Trump is so colossally incompetent, unfocused, racist, and stupid that his administration has not been able to successfully guide any legislation of consequence through Congress. More surprising still, Ryan and McConnell have proven unequal to the task of wrangling the Republican majorities into passing legislation either.
Scenario 1 would have been awful and 2 was probably a pipe dream, but that we are living through 3 sets a new problem into relief. What does it mean that a Republican Party can control such majorities and the White House and still not produce? Put another way, what is the purpose of the Republican Party?
David Potter, in his remarkable posthumous work The Impending Crisis, said this about the Whigs and Democrats in the late 1840s:
Relatively unencumbered by ideological mission, the two parties did not have enough intellectual focus to offer voters clear-cut alternatives. Thus they failed in one of the classic functions theoretically ascribed to political parties. But if they defaulted in this way, they performed admirably another equally important if less orthodox function: they promoted consensus rather than divisiveness. By encouraging men to seek a broad basis of popular support, they nourished cohesiveness within the community and avoided sharpening the cutting edge of disagreement to dangerous keenness.In that case it didn't last much longer. Eventually slavery drove a wedge between the Northern and Southern wings of both parties, destroying any hope for national popular support. The Whigs fell apart by 1852. The Democrats split in 1860 and barely survived the war intact.
The current Republican Party proved they could win a national election, but only by merging contemporary conservativism to right-wing populism. (And even then, they still lost the popular vote.) In making such a bargain with Trump, they sacrificed whatever ideological coherence they had previously held on to. Nor does their appeal consist of "promoting consensus," to use Potter's words. Extraordinarily, the Republican Party, in firm control of the government, does not seem to be doing any good for any constituency. It is suffering an existential crisis in the midst of its electoral triumph. If things continue as they have, the party could fracture.