I'd guess the stopped car on the right flashed to let them in. Often see people flash a car to pass them without checking whether it would be a safe maneuver -

I'd guess the stopped car on the right flashed to let them in. Often see people flash a car to pass them without checking whether it would be a safe maneuver - most commonly where a car waiting to turn left into a side road flashes you out of the sideroad, ignoring the fact that there are cars passing them to their right.