Headscratchers / Star Trek Discovery Short Treks E03 "The Brightest Star"

• If the Ba'ul are already interfering with the Kelpiens, then the Prime Directive shouldn't apply, right?
  • Hard to say. We don't know if the Ba'ul have warp and if that matters.
  • The Ba'ul have warp, but they're native to the planet. So, if the Ba'ul told them to leave, then that's what Starfleet will do, usually
• The Prime Directive is supposed to prevent the Federation from messing with another planet's development (mainly to prevent anyone from playing god, and to prevent anyone from e.g. forcing their own values on different cultures, but it's often used for any involvement, even with warp capable species who just aren't Federation members). Then why were they allowed to take Saru? Earth would be very different if aliens had, say, grabbed the Wright brothers (or their father, or great-grandfather)?