Even though /r/the_Donald posters tend to be much further to the ‘right’ than Dr. Peterson himself, he is still immensely popular there. But not just on /r/The_Donald; he’s popular among intellectual types of all political stripes, from rationalists who lean left, to reactionaries on the far-right, and everywhere in-between.
Dr. Peterson is popular among the far-right–in spite on many occasions in his videos disavowing the alt-right and identity politics–because, crucially, he lends a veneer of academic credibly to right-wing ideas, where such credibility is lacking and much needed. It’s not news that academia has a strong left-wing bias, so right-wing academics, especially ones as outspoken and articulate as Dr. Peterson, tend to be something of a rarity. Credibility is extremely important, and Dr. Peterson excels at exuding competence, whether it’s his memorized recitations of Biblical stories, to his encyclopedic knowledge of the history psychoanalysis. Dr. Peterson’s success is an embodiment of his own philosophy, which puts competence at the top of all social hierarchies.
Second, the self-help angle is really important. Many of his fans don’t seek to wage ideological war but merely want to improve their lives and ‘clean their rooms’. Rather trying to paint over adversity with affirmations and self-esteem, Peterson’s approach, borrowing from Nietzsche and Schopenhauer, is to acknowledge that life is tragic and full of suffering and than with this information take steps to rectify it. People are drawn to this counter-intuitive, unorthodox approach.
A criticism of Dr. Peterson is that his ideas are not original, but seem profound to those who have otherwise never been exposed to them, yet are banal to experts. The truth is, the vast majority of academics don’t have profound or original ideas. Dr. Cornel West is very popular; name one profound or original idea he has produced. It’s so rare that when someone does it, they may get a call from some Swedes offering a million dollars. His ideas don’t need to be that profound or original–they are good enough to have an impact on the thousands of people exposed to them, and that is good enough. But also, his interpretation and exposition of the concepts is original. The ability to communicate ideas is as much of a skill as the ability to produce them.
He has a scrappy physical appearance and temperament, which I think makes him more likable and easier to relate to. If he were overweight, then maybe he would seem gluttonous and slow. Even something as seemingly trivial as having curly grayish hair helps, because he looks the opposite of the slick-haired, square-jawed salesman. Details matter because they help us subconsciously form our opinions of people. In his videos from early 2017 when he was lecturing at the University of Toronto, he is wearing jeans with an array of keys hooked from a chain attached to a belt loop and his sleeves are rolled up, much like that of a groundskeeper or a janitor, but this is contrasted by a sports jacket or a dress shirt, signaling a sort of blue-collar solidarity juxtaposed with high-minded intellectualism.
Generosity. He produces hundreds of hours of content free of charge. Some complain that he charges $9 for a personality quiz or that he makes too much money from Patreon donations. Yet how is it any less ethical that Dr. Peterson profit from his work from people who voluntarily donate, than an overpaid celebrity that stars in yet another formulaic movie that barely makes back its budget and gets paid $10 million anyway.
Similar to Scott, he is receptive to opposing views rather than shouting them down or dismissing them. Persuasion is not about browbeating the viewer about how ‘right’ you are, but about making an argument that is so convincing that the viewer/reader is left with no other option but to agree, and voluntarily does so, by answering all doubts. This excellent video explains it more detail:
He first explains the justification for Marxism and postmodernism, but then explains how it’s wrong. Some may say it’s wishy-washy, but the the strategy works.
Descriptive language and metaphors that invoke images in the listener’s mind. In a recent lecture he says “thoughts will enter the theater of your imagination,” regarding why people are easily distracted when they try to study.
He’s disarming and patient. There is no pretense of superiority or aloofness. In a viral video in which he debates trans activists, he doesn’t berate them but rather tries to reason with them, as futile as that proves to be. Unlike Bill O’Reily, Bill Mahr, or Rush Limbaugh, with the exception of an anti-Peterson sub, one would be hard pressed to find anyone who truly hates Jordan Peterson. No one says ‘that Jordan Peterson is a real piece of shit,’  which cannot be said for many public figures.
 Edit: one author does just that