Here is the official video for "The Weeknd & Ariana Grande - Save Your Tears (Remix)". The video you linked is not the official video, and Ariana Grande doesn't even sing on that version. The channel which uploaded it is full of mislabeled videos which cut off halfway through. Very strange, perhaps they are farming clicks for ad revenue?
Anyway, here's the most likely way we arrived at this recording: The vocal track was recorded by the singer while listening to the backing track, and she sang it in the right key. Then a producer either a) tuned the vocals to the wrong key, or b) changed the key of the backing track after recording. Now the backing track and vocals are in different keys and it sounds terrible polytonal.