Peterson is popular with the alt lite, 4chan incel demographic because he validates them, and tells them what they want to hear. I grew up with a father who both physically and ideologically is almost identical to Peterson, however, so I don't find him particularly compelling.

There are a lot of scared, angry, alienated young and middle aged men in the world at the moment. These men are alone and most likely will never have partners, reproduce, or in most respects experience the positive aspects of communal life which previous generations did. They look out at the world and they see a chaotic environment full of people who hate them and seem to want to destroy them, primarily for the crimes of their ancestors.

Against that backdrop, Peterson comes in, and while he does tell them to take responsibility for their situation, he also tells these men that said situation is not completely their fault. He talks to them about feminism and cultural Marxism, and about how the deck has been stacked against them, and in interviews in various places, he even seems to rhetorically go into battle against feminists.

Said men therefore begin to see Peterson as their champion. He's a folk hero for them. A twenty first century online Beowulf, who has come in their hour of need to slay Anita Sarkeesian and her Gorgon sisters. He's even made friends with Sam Harris, which just proves that he isn't only a hero for lonely Christians, but he can be one for the atheists as well.