I remember my IT teacher giving a lecture on this once.
On the original typewriters, the keyboard layout was different, and that layout allowed people to naturally type pretty fast. However, the fast typing often caused the keys to jam, so the keys were rearranged to the QWERTY position so people would type slower to minimalise jamming (I can't remember exactly why QWERTY slows people down, something to do with how the fingers worked or something I think). But since we're all so used to the QWERTY keyboard now it doesn't really matter anymore.
On the original typewriters, the keyboard layout was different, and that layout allowed people to naturally type pretty fast. However, the fast typing often caused the keys to jam, so the keys were rearranged to the QWERTY position so people would type slower to minimalise jamming (I can't remember exactly why QWERTY slows people down, something to do with how the fingers worked or something I think). But since we're all so used to the QWERTY keyboard now it doesn't really matter anymore.