Inventor Thomas Edison did not discover electricity, nor did he actually invent the light bulb. What he did in 1879 was invent a longer-lasting light bulb that was more reliable. His first successful lamp stayed lit for 13.5 hours.
The light bulb itself had already been invented half a century before Edison came up with his improvements, but that does not make what he did any less spectacular. He needed to find the correct filament for making the bulb work well. He had to establish a parallel circuit that allowed voltage to be maintained, an underground network for conduction and sockets that had on and off switches. None of these discoveries had been made before that point, and they were all vital to a successful light bulb.