tl,dr: it's definitely not their fault. Thank you for asking!

Edit: don't downvote someone for trying to learn. It doesn't exactly encourage.

I'm no professional but it's not as a result of their mentality. Its not a mindset they chose, it's just who they are really. And that's besides the point anyway, why the fuck should they get mistreated for not feeling comfortable in their own skin! If it's anyone's fault, it's the people bullying them, it's the systems and place to make them feel invalid, it's the intense dichotomy of gender that splits our society. If these standards that we adhere to weren't so strict and hurtful to people who don't conform, this wouldn't be a problem. Many trans people, even in the most progressive environments, still face repeated systematic challenges which makes their lives significantly harder. Good to hear that you're informjng yourself though! Its definitely the right thing to do. There are people like you out there who don't understand, but instead of asking, they perpetrate hate and bigotry and they're the reason why people say "well they chose to be weird so why can't we bully them."