It's actually very simple.
I'll give some key reasons.
Social
A lot of incels are autistic, and lack a life purpose. The way the current society is set up made it extremely hard for us aspies to socialize and have common ground with normies.
In totaliartive regimes, like the USSR, Maoist China, Nazi Germany etc, all to be a 'good citizen' you only needed to show your patroitism and work hard. Making fun of eugene for being a nerd devoted to working for the sake of the country would have never been accepted. Plus race/country have very low bar of entry, that is one factor we can use to find common ground with other people.
"Guarantee of a wife"
Fascist countries tend to have rigid gender norms, that incentizes and requires women to marry off 'losers', that is, the average man. In free love environment, like the animal kingdom, women only pick the very top men
The need for equity
The big ironic factor is that the far right tends to care more about true equality than the left. The left thinks that everyone is the same, so if you struggle then it is your fault. The far right recognizes that there are different races that are good at different things, and by sergerating them, they can interact fruitfully with other peoples without causing conflicts.
Power and pride
It's common knowledge that nationalists really dodnt have much going for them, hence, the r/beholdthemasterrace thingy. Theree's a saying "when you have nothing to be proud of, at least you can be proud of your country".
Race
Races are inherently unfair. Some are smarter, some are better at sports. That has led to unfair interracial statistics, which is 90% source of ethnonationalism in recent timess. I've been around black/asian/white nationalist spaces and lots of them are mad pissed at their own women dating other races of men, which is reasonable complaint to make.
Leftist spaces are simply shit
Leftist spaces are shit. I've been banned for having a pepe frog picture in r/antiwork discord. They tend to be shallow people who only look at the surface. Oh, you say the "n word"? You must be Hitler reborn!!! The far right spaces doesnt do that. If you speak something stpuid you may be flamed like here or 4chan, but you wont get downright banned for it.
Just look at how many people call the GOP fascist, despite the fact that they are for small government and companies. Or how sanders is a communist. The "left and right" acceptable by mainstream, is simply NPC-ish.
