Why? Because young people everywhere (red states and blue states) all like sex (gay and straight), drugs (legal and illegal), and music (country, hiphop, pop). The top 100 list on Apple Music is 50/50 country and poppy hip hop, for example.
The main reason young people affiliate with socially conservative groups (churches, etc.) is to signal membership in a system engineered to get them into a relationship (aka attraction, flirting, sex, etc.). A young male joins the group and immediately gains credibility as being a good person, etc. A young female joins the group and immediately can relax because the males she's meeting are vetted via their membership in the group. A young gay person joins because his/her young gay friends are also members, and they can use the org as cover to spend time together without needing to come out.
Institutions have a label, but their purposes can change very rapidly. Humans are superb at leveraging institutions to achieve their goals.
There are going to be some groups of young people who claim to have highly prejudiced beliefs, etc., but those are fairly common and rarely hold up to scrutiny as the belief holder gets older.
In other words, there is not any sort of youth-oriented grassroots social conservatism in the US. There will always be economic populism, but increasingly there is not a "golden era" in memory for young people to harken back to. Chances are among the stereotypical Trump demographic things were never very cushy economically, and chances are very high that all have had good friends who are African American, latino, hispanic, asian, or any variety of multi-racial backgrounds. Chances are they've had a crush on a multi-racial person and consider the person's humanity far more heavily than their isolated grandparents did (who likely never had many peers or friends from other groups).
I think the Internet will take us to a new age that looks strangely like a much older one.
New social conservatism on the Internet does not look like old social conservatism because it is out of living memory. It is a return to what I could only describe as aspirational Victorian Era with updates from the Diamond Age. It pines for a new Golden Age. Exploration and feats of strength. Great Men and Women. Charity for the weak. Gifts for the strong. Perhaps people can earn points to elevate themselves in the class system, which you can think of as an immersive MMORPG with AR but with real life consequences and rewards. There would be tea, iron railings, umbrellas, crumpets and art galleries with beautiful art once more. All UPVC would be replaced with timber.
The neoreactionaries would produce a government and society focused on artificial intelligence, advanced genetic engineering, nuclear power. The history books would be written to explain to schoolchildren that an evil cabal of religious marxists attempted to wrest control of the West. You may have formerly known these people as 'Social Democrats' (shudder). The entire history of the 20th century would be reframed in Spenglerian terms. A typical school exercise might read "Compare and contrast the 3 Demotic Terrors: Democracy, Fascism and Communism" and it should be understood that democracy and religion would be considered socially inappropriate since they were the reason the Third World War began. You can believe in them, but proper people don't. We shall also have an excellent array of hats to choose from, far from the dismal hatless tyranny we reside in today.
Since this world knows a vast amount about people's preferences, voting is not required. Your interests are duly noted and factored into a personalization of your local government's offerings. You are of course free to leave to the next Seastead or Landstead (formed by Climate Change and Demotic Warfare!), since each group has different interpretations we take the ability to opt out seriously.
Would this be a dystopia? Or a radical improvement on our age?
This is largely because our powerful class has found ways to circumvent it democracy... no matter which party wins, things will stay pretty much the same. Voter turnout reflects this.
I find your point interesting. I think the deep question at the heart of it has to do with the idea of "how important are rules if we can just change them as we go and be better off?"
Economic examples abound, but we've also seen our system of laws evolve into a vastly weakened rule of law such that law enforcement can simply choose from any number of laws that a person might have wittingly or unwittingly violated. This is not an outrage because we are trained to trust those in power.
Notably, Justice Sotomayor on the SCOTUS is "liberal" in some ways but very compliant when it comes to issues of law enforcement privilege, etc.
You are also out of touch with reality like Altman admitted about liberals not understanding almost half of America. He was right that they've totally ignored their motivations. The Trump supporters are mostly Republicans and people in rural areas. These people have kids, raise them to mostly have similar beliefs, watch similar media that's pro-Right, and often vote for same people. Trump supporters in Mid-South are across all ages with more older ones but plenty in 20's-30's. Almost all the rural people I've asked are pro-Trump because they'd never vote for Democrats but especially not Hillary. They think Trump is more likely to deal with things they care about than a "snobby city-dweller" who doesn't care about them at all.
This will take a long time to die off thanks to the effects of isolation and close-knit communities on new generations. It's not going away in 4 years. Best thing to do is get some Republican candidates in that tap into that who aren't as dangerous as Trump for next election.