If the Light of Truth (Sat) is an Eternal Light, then it can never be overcome by darkness. Any kind of "not-seeing" of the Light is only a belief maintained through and by ignorance.
Therefore the Guru does not remove the darkness to reveal the Light (for the light is Ever-Revealed, Never-Concealed).
The Guru only removes this belief of there ever being something able to cover the Eternal Light.
The Guru removes ignorance, the only darkness there is, and it is an illusory one.
Jai Guru Dev!