As always, I strongly suggest listening to this track before watching my music theory analysis video (if you are not already familiar with it).
For your convenience, I have pulled the sheet music, chord charts, and any other especially salient diagrams from the analysis and posted them below.
1: Intro Unusual chord shape plays the role of V7 in the key of B minor.
2: Verse Chord shape recontextualized as the bII in the key of A minor.
3: Chorus (1/2) The Fmaj7 contains the notes of C major, which would act like a bII chord back to the chorus key of B minor.
4: Chorus (2/2) Using a B7 to establish a 'pivot key' of E minor justifies the direct change from Bm to Am.
5: Post-Chorus Switching from the key of B minor to its relative major key, D major.
6: Bridge Dmaj7 and Cmaj7 are a relative major nod to the song's two main minor keys.
7: Outro Returning to the Bbmaj7 chord (the most flats), then jumping to the Dmaj7 chord (the most sharps).