Let’s make this a meme.
The four horsemen are Jordan Peterson and Ben Shapiro (who skew right), and Dave Rubin and Sam Harris (who skew left).
All of their popularity has surged in the past year, they all seem to share similar rational-minded centrist/moderate/pragmatist views, they all have huge social media presences, and they have all done interviews with each other.
But others include Eric Weinstein, Steven Pinker, Sargon of Akkad, Gad Saad, and Jonathan Haidt.
In 2017 during the numerous campus protests and such, the alt-middle/center rose to preeminence by going after easy SJW targets and promoting ‘free speech’ and other classical liberal ideals. It’s much easier to convince ‘fence sitters’ that SJWs are bad, than it is to instill in them them alt-right concepts. These centrists’ angle is to eschew ideology and identity (which are fixed) for rationalism and empiricism.  The alt-right, which rose to preeminence in 2015-2016 during the rise of Trump, sorta found itself in 2017 adrift, without a similar ideological anchor/rallying point. The alt-middle has a monopoly on beating up on SJWs, but the alt-right doesn’t do that game as well and are more focused on themes such as identity, IQ, religion, nationalism, race, etc. that tend to be more controversial (Dr. Peterson, to his credit, incorporates some of these elements into his talks).  In the span of just a year, the alt-right went from being a viable political insurgency in America, to being almost irrelevant now. Most of the major alt-right figures have either dropped off the map or have been subsumed by the alt-lite. A few months ago, Richard Spencer stooped to having to do an interviews with Sargon, of all people, just to show he was still relevant. How can the alt-right fix itself…I don’t know. It would probably require some sort of national catastrophe or maybe a Trump-like figure that is able to rise to political office.
 For someone like Ben Shapiro, who is part of the moderate right, his values are formed by empirical evidence and other external factors. But for the ‘hard right’ (such as Christian right and paleocons) their values are intrinsic to their identity, not based on the external. Ben Shaprio may cite statistics for why gun control is wrong, but for the hard-right, guns are a part of their identity and culture, and thus don’t need to provide a rationalization or justification for why they should have guns. When such external evidence changes, so too may the values. But for the hard-right, their values don’t change, in much the same way a person’s skin color or race does not change. This is similar to the hard-left versus the classical-liberal/centrist left.
 Trying to answer why science, psychology, and pragmatism are an ‘easier sell’ than nationalism and identity will probably require another post. The obvious answer is, because American society is already left-wing, such as through school and cultural indoctrination, the leap from campus-liberalism to Jordan Person pragmatism is a lot shorter than the leap to Jared Taylor conservatism.