Umm his label always discounts singles from their artists. Nick has nothing to do with it.
Also these discounts always last for 2 weeks and that's it. I don't understand why is it such a big deal? Btw his song was released 2 months ago, it's not like it was discounted in the 1st or 2nd week.
And FYI the song's been discounted for a week already, and it literally didn't move one spot. The Carpool Karaoke pushed it to #13 and it was put on Hot Tracks this morning, that pushed it to #9. Sure the discount had to help a bit, but it's not the solo reason it surged this much, like you are making it seem.
Actually Island is doing a great job with this, and most of you can only wish your fave's label does something similiar.
Last week : discount + Carpool Karaoke
This week : discount + Hot Tracks on iTunes + BBMA performance
Muse be very close to top100 combined.
top 5 coming 
jk yikes can you imagine that.
So late