>>4151688Ginny is too firmly attached to Harry in the source material to produce a lot of interest in pairing her with other people, especially for people whose introduction to the IP was the movies, since pretty much the entire rest of her character was omitted, and Luna is... Luna. Her characterization especially for movie-only people, with how completely spacey she is there, makes her more challenging to write in a romantic context and chemistry awkward. Hermione is the standout because she's a much bigger protag and there's so little chemistry between her and her canon love interest.
Then add to that Bellatrix being sort of tailor made for fanfiction. She has an extremely strong personality that extrapolates well into common fanfiction tropes (dominating, possessive), she's foeyay, her pureblood fanaticism makes that even more poignant given Hermione being muggleborn (borderline star-crossed). Her background framing makes her an interesting target for exploration in fanon. By that I mean that with her comes a whole big interesting tangle of characters and narrative opportunities: Narcissa, Malfoy, Draco and their situation, Andromeda's situation with Nymphadora and Tonks, pureblood aristocracy and family dynamics, the innerworkings of the Death Eaters and various members of that side, a political marriage to Lestrange, Sirius, Voldemort, went to school alongside Rita Skeeter, Arthur and Molly, was locked in Azkaban.
In comparison, Ginny brings almost nothing new to the table. She hangs out with/knows the exact same group of people Hermione does and has gone through the exact same events. Luna is much the same. It's hard for them to compete as interesting options with a heavyweight like Bellatrix. Not that I mind the other pairings, it's just pretty obvious why relatively few people pick them.
