I'm sure mostof you have noticed that far madami popular than the Cosette/Marius ship is the Éponine/Marius ship. I don't mind the ship, but I often find people asking why Marius was so blind to Éponine's love, never considered her and chose Cosette over her. Here are a few reasons:
1. First off, you have to know that the musical isn't completely honest with the character of Éponine, nor the relationship she shares with Marius. The musical had to make several altercations to the characters, including breaking the relation between the Thérnardiers and Gavriche (he is their son), and discarding the character of Azelma (Éponine's little sister) completely. For the musical, Éponine's character was altered. In the book, Éponine is most definitely not a beauty, missing a few teeth, bags under her eyes and is a regular drinker, understandable traits for her character as she has been pushed into poverty. One key trait not made present in the musical (though added and portrayed beautifully sa pamamagitan ng Celia Keenan Bolger) is that Éponine is slightly insane, disregarded sa pamamagitan ng her parents and watching her childhood rival become everything she wanted to be. The musical cuts out some of Éponine's unlikable personality, making it harder for the audience to understand why Marius wasn't head over heels for her. The musical also added madami to the relationship of Marius and Éponine: in the book, Éponine and Marius were not friends, madami acquaintinces live in the same building. Éponine was instantly attracted to Marius, although only seeing him a couple times. She would often follow him around, but he only responded to her attempts of conversation to ask her for favors. If you're wondering why he treated her like that:
2. It's because of social class division. In the book (and touched on in the musical), Marius is known to come from a rich family. His grandfather is rich, and while Marius refuses his grandfather's help (they don't get on well) and lives in a dirty, disgusting apartment (Where the Thérnardiers also reside), it is still very clear with his well groomed appearance, nice clothing and proper speech he is a gentleman. Éponine does not fall in this class at all: her family is poor, her clothes are ragged and torn, her figure is frail and thin and her speech is slurred and riddled with slang. She also drinks alcohol, something not considered proper for a girl of her age. Naturally, during this time period, the rich and poor had a clear division. The rich looked down upon the poor, and most of the time wouldn't dare to speak to them. Éponine was fortunate enough that Marius responded to her words respectfully. However, he would never consider her madami than a friend at most. A relation between a gentleman like Marius and a kalye waif like Éponine was unheard of at the time. Éponine herself was aware of this, walking behind Marius while she led him to Cosette's residence so he wouldn't be slandered for being seen with the likes of her.
3. Theoretically, Éponine's pag-ibig for Marius may not even be pure. As stated earlier, she was attracted to him on sight (Believe or not, Cosette and Marius had a few meetings before he became attracted to her in the book). Think about it: Éponine never had a chance to experience real love, being overindulged and then cast aside sa pamamagitan ng her parents, and when she met a kind face for the first time, she attached on to the only thing she knew to be good. I think Éponine was madami in pag-ibig with the idea of love, something she barely knew, rather than in pag-ibig with Marius himself. This explains why she was so upset with Cosette taking Marius: Éponine was cruel to Cosette in her childhood, who still knew pag-ibig from her mother, even as miserable as she was. Then, the tables turned, and from Éponine's point of view, Cosette once again steals pag-ibig away, only this time it is Éponine and not she who is miserable. Éponine is so desperate for love, she decides that if she can't have it, no one can, and she leads Marius to the barricade in hopes of dying with pag-ibig (getting him shot dead). She eventually decides she wants to die first, and saves him from getting shot. As she dies in Marius' arms, she is content, for she has finally experienced a warm embrace in the arms of the man who showed her love.
I hope this gives some insight to those who are baffled sa pamamagitan ng Marius' choice, which, I admit, is pretty strange if you've only seen the musical. Hope I helped!