None of the Soyjaks are conventionally attractive in any way. Only certain subvariants, like Perceptive Chud, could be counted as attractive. Strangely, however, these aren't the ones which are lusted after.
I believe it is a similar phenomenon to the fascination some men have with "femcels" (compare: Tomoko), though another possibility could be a sort of "bad boy" or dark triad effect with chud specifically. He is, after all, sometimes depicted as a hateful, violent and unsympathetic school shooter type. Murderers and serial killers are well known to be admired and lusted after by many women, even if they are not really conventionally attractive.
As for the male fascination with female variants: Too much gooning on /nate/ and the jarty.