Iggy isn't Taylor Swift or Katy Perry
She isn't going to just release a single and have it fly up the charts even if it is a lead single. She's still establishing herself.
If she did a standard release (Monday or Tuesday with an iTunes banner) then she would have been Top 10 by now, but she will need to wait a bit for Radio to catch up and a MV if she wants to get to #1.
The song definitely has more replay and hit value than Black Widow and that song did great.