In the early 20th century, Alfred Wegener posited that the earth's continents are in a constant state of slow motion, and had at one time actually formed a single landmass. He pointed to the obvious similarities in the geological record on different continents, as well as the fossil records, to prove this.
The move was met with bitter criticism and outright hostility by the scientific community. Leading geologists argued that Wegener's theory was absurd, and that the anomalies he was reporting could be explained by other means. The pervasive theory of the establishment was that a series of "Land Bridges" allowed species to travel to these far-distant shores, where they promptly died and left their bones and fossils behind.
Every time more evidence came to light that challenged this view, the scientists would simply draw another land bridge on the map. It got to the point where there was more land than water! Eventually of course, Wegener was proven right, and the land bridge theory was relegated to scientific history.
Human nature leads us to cling to familiar, comfortable notions, even in the face of overwhelming contradictory evidence. We tend to reject the unfamiliar, uncomfortable, and novel. Like the science community at large, we will stick our heads in the sand when a person like Alfred Wegener comes along to challenge our preconceived notions.
For the past several decades, a similar phenomenon has been festering in the Republican party.
For the GOP, America is a land of WASPs (White Anglo-Saxon Protestants). They watch 50's sitcoms like Leave it to Beaver, and imagine that America is still the perfect suburban nation that it was then (hint: it never was). As America's demographics have changed, and that vision is harder to maintain, Conservatives have faced a choice: alter their perception of the country, or refuse to accept change.
They've chosen the latter.
The evidence of this is rampant. From rejecting the results of an election to lambasting immigrants as murderers and rapists, the modern conservative movement has turned its back on today's America, and has rejected out of hand any suggestion that what they believe is wrong. To them, the white middle-class America is still alive and well, but under threat from "the other." If it doesn't fit the narrative, it must be wrong.
Trump managed to harness this view and turn it into a new political weapon, by presenting himself as a part of that view. He legitimized the opinion that the United States is predominantly White, Christian, and Conservative, despite all evidence to the contrary.
The further the nation gets from this vision, the harder it will be for conservatives to maintain their illusions. Even now, they are advocating for limits on the rights of those who disagree with them, merely so they can continue believing their fantasies. As time goes on and the country continues to grow in diversity, it will become even harder to maintain this façade.
Eventually, there will be a fracture, a break that results in either a major correction, or a complete splintering from reality. Conservatives need to start appealing to the world as it is now. They will not survive if they continue to reject the world that they now live in.