It didn't

If your history books did not teach you about how fucked up this world is and how fucked up people are, then you read the wrong history books.

The books, I read fully prepared me for this bullshit. None of this is a surprise, nor should it be.

Honestly the post should say ‘history classes’. Classes tend to cover a broad scope as do the textbooks they assign. I certainly have read larger picture nonfiction work, but I think it’s more common for books to cover more specific periods of time.