5.15Voice leading explains why ii–V–I works so well

Dm7:

D F A C

G7:

G B D F

Cmaj7:

C E G B

Focus only on:

Dm7:

F C

G7:

F B

Cmaj7:

E B

Look:

C → B

then stays B

F stays F

then F → E

Very smooth.

Functional harmony and voice leading reinforce each other.