It could be because of its engaging plot and well-developed characters that draw readers in.
Well, they have a really interesting dynamic. Kotegawa is a strong - willed and often strict character, while Rito is more of a clumsy and kind - hearted guy. This contrast makes for great storytelling as they can play off each other's personalities. For example, Kotegawa can be the one to keep Rito in line, while Rito can show Kotegawa a more relaxed and fun side of life.
Maybe it's because they have interesting plots and characters that appeal to a wider audience.
I really don't know. 'Y novel' in 'why ru' could be a made-up term or a personal abbreviation that only the creator of the phrase understands. Without more context, it's hard to say.
Rito is also quite popular. He often finds himself in all sorts of comical and romantic situations. Another popular character is Haruna, who is a bit more reserved compared to Lala but has her own charm.
Lala Satalin Deviluke is quite popular. Her outgoing and energetic personality, along with her unique alien features, make her stand out. She's always getting into all sorts of crazy situations and her love for the male protagonist is very endearing.
Well, a lot of the popular 'To Love Ru' fanfiction pieces are those that expand on the comical situations in the original work. Maybe they take a single gag from the anime and turn it into a full - fledged story arc. Others might be centered around the character development of the female leads, like how they adapt to life on Earth and their feelings towards the male protagonist.
One popular 'To Love Ru Lacospo' fanfic could be those that focus on the unique relationships between the characters. For example, some might explore the development of the relationship between Lala and Rito in more depth than the original story. Another type could be the ones that create new adventures for the characters in different settings.
The specific reason why Jia Erhu and Wen Ru did not serialize it was not clear. As a fan of online novels, I can only answer questions about novels that I already know, but I can't provide the latest information about novels.