The character ل can be used as a preposition. The preposition means "for".
The word أن means "that".
When you combine the preposition ل and the word أن together, It becomes the word لأن. The preposition and the word are connected together because the preposition ل is always connected to the next word.
The meaning of the word لأن is "for that" but the actual meaning is "because".
Now, There are two ways to say "because you".
You means انت
So, (Because you) = لأن انت (it is understandable but it is not commonly used)
The other way is to use connectivity of pronouns in semitic languages. I mean pronouns are able to be connected (embedded or compressed) to a word. In this case, The pronoun will take the form of an object pronoun.
To learn more about object pronouns you can watch this video. I've made it myself: https://www.youtube.com/watch?v=LiypiNzmc80