Help me understand this circuit - unexpected LED behaviour
The blue line shows how the current flows when the switch is open and the motor is off:

When the switch is open, the electrons can only flow by going through the LED. Very little current goes through the LED, so very little current can flow through the motor.  The LED lights because it only needs a tiny bit of current.  The motor doesn't turn because it needs a lot of current.
This is how the current flows when the switch is closed and the motor is on:

When you close the switch, the electrons prefer to go through the switch rather than through the LED.  Lots of current can pass through the switch so the motor turns. Nearly all of the current goes through the switch, though, so the LED doesn't light up.