A non-lubricated pulley makes the rubber belt rotate more because there is more friction between the pulley and the belt.

Energy was transferred from the rotating pulley to the rubber belt.

The energy from the rotating rubber belt was transferred to the generator shaft.

The rotating generator took this energy and turned it into electricity which was transported through the wires
 to light up the bulb (light energy).

On the other hand, lubricating the pulley did not create any friction between the rubber belt and the pulley.

This in turn prevented the belt from rotating well.  Thus, the rotational energy from the pulley did not get transferred to the generator.

Therefore, no light energy was produced and the light bulb did not get lighted.