Why would speaking the same language cause people to form a closer
relationship? *

Because if you speak in same language you'll understand what does you peer is saying for example, you need help with a homework and if you don't know English, you can't communicate with your classmate or teacher but if you do, you can easily communicate with them. Your language helps you to express your feelings to other and if everyone speak the same language people can communicate easily and comfortably which cause people to form a closer  relationship.

glass wants to live in a world of super heroes and villains. he have lived all his life trying to be responsible for the creating the origin story of a super hero; he schemed and caused many incidents (many of them fatal) hoping that someday someone with superpowers would show up and save the day.

he knew himself very much. he saw himself as a villain of a real-life super hero story. he was aware of his strengths (more than smart enough for being manipulative and scheming) and weaknesses (having fragile bones and having to rely on his mind to succeed).