Opportunity is missed by most people because it is dressed in overalls and looks like work. Thomas Edison
In the 70 years before Edison, there were at least two dozen inventors of the light bulb. As did each of his predecessors, Edison greatly increased the life of the bulb and decreased the cost. But others dramatically improved upon Edison's design and the incandescent bulb we recognize today was invented by William Coolidge.
Edison had a much greater contribution to the light bulb then its design. He invented an entire system for electrical distribution. Or, more properly, he took dozens of other people's inventions and integrated them into a power plant, transformers, light bulbs....
When he started all of this, it was obvious that it would work. All of the pieces had been demonstrated. That said, it was a tremendous undertaking to integrate and modify them in a cost effective manner.
There were also constant improvements to be made. For example, Edison held dozens of patents for electroplating because he needed improved processes to join the bulb's filament with electric wires.
He also had to displace the gas torches and pipelines that already ran through cities. Political deals, business deals and questionable deals were all a part of 'inventing' the light bulb for Edison. There are many anecdotal stories of sabotaging gas lines, bribing public officials and creating gas torch fires that while perhaps untrue, certainly add flavor to the story.
For Edison, it could BE different, required 99% perspiration.