Edison may have been a great man but he had many very smart people working for him who never received credit for their inventions. That happens in many labs.
It has always been that way. I work with an inventor but since he worka foe a company, all his inventions are owned by the conpany and not him. He agreed to that stipulation when he took the job.
I know you will now say that this is theft or something of the sort and this is how the rich stay rich. But it is a better way than him than trying to sell his idea and getting no where. He at least gets a nice salary with no need to create a business from the ground up.
It is not perfect.