Good OP -- some stuff I agree with, some stuff I'm less sure about.
I believe the causality goes backwards: they became WNs as a direct result of sexual frustration.
I think that young men who are attracted to fringe political movements are attracted to them primarily because they see upward mobility within their society as blocked off for them. They are unable to earn a living that enables them to undertake rites of passage into adulthood -- owning property, working, marrying, becoming fathers. This prevents them from achieving an appropriate status in their communities and therefore denies them a dignified existence. They therefore are attracted to movements that offer them the status within a political sub-community that they are denied in the society at large; can be persuaded by visions of an alternative future society in which they will have a greater chance of attaining proper status; and have little to lose in their present community and so are less susceptible to the threats of ridicule and ostracization that often faces political outliers.
So I think a lot of WNs become WNs due to fear of loss of status, combined with a lack of social connections and a susceptibility to "charismatic" leaders.
There are some guys in the WN movement who appear to have basically normal sex lives. Sven from TheRightStuff is one such example. Also, it has been noted how often WN leaders -- like leaders of other fringe political movements or of cults -- have multiple partners often procured from amongst the wives of followers. David Duke was notorious for this, and Matthew Heimbach has been shown to have similar tendencies. There have been rumblings about Richard Spencer in this regard too. I have even seen people make the argument that rising to prominence in WN and similar movements is an elaborate "mating strategy" in which men gain status within a certain sub-culture in order to cream off the partners of more docile followers:
https://traditionsofconflict.com/blog/2018/1/31/on-secret-cults-and-male-dominance
I guess this gets to the question of just how central the desire to fuck and procreate is to all or any male behaviours. I am open to the answer that it is very, very central. But if that's true then it applies just as much to a commie or to a camgirl masturbator or an EDM DJ as to a WN. "For some reason", the Frankfurt School and Freud have not been as interested in belittling other political movements by "trivializing" them down to a set of psychosexual (leaving aside the fact that, as I just said, I don't think such neuroses are in fact ever trivial). I am very sceptical about both Freud and the Frankfurt School particularly on this topic.
The Authoritarian Personality shows how unscientific and histrionic the latter could be in its conceptualization of the political Right -- you don't have to be a WN to suggest that maybe the ethnic identity of its members plays a role there.
Can you picture yourself doing this? Obviously not. Most likely, you'd use your Saturday afternoon to chill with friends, have a girl come over, prepare good food, watch a movie, work on your novel... Do cool, funny stuff.
If WN is just another "cope" hobby then how is it any different from going on Antifa marches, studying the works of Lenin, being really into MMORPGs, etc..? Why do certain people choose WN and not one of the others?
Also, I think most here would agree that
[this is not] a coincidence, or a result of their ideas.
but I would push back a little when it comes to the latter part. Women are definitely turned off by extreme right-wing political beliefs, moreso than any other type of ideology. Women are very consensus-driven, concerned about status, and morally oriented towards avoiding harm in the weak. I have noticed that dating is much tougher since my politics drifted Rightwards, even though I am more just some kind of populist / anti-capitalist conservative rather than a WN. I think WNs would probably agree with this assessment, yet they persist in their beliefs despite it being a "bad" dating move.