Alot of the credit is the result of early mergers and DC aquiring properties from elsewhere they didn't create.
Like Plastic Man is originally from Quality comics. Most of their war era characters are also purchased.
The reason you had so many early DC characters with legacy versions (two persons that both share a hero identity) like for example Jay Garrick and Wally West both being known as the Flash or Richard Grayson and Tim Drake both being known as Robin, is because DC loved to buy other companies and reboot their characters.
Thats not what happened with robin... just using him as an example of a legacy identity.
They were notorious for rebooting shyt. Thats why there are multiple Atoms, Hawkmans, Lanterns, Flashes, or just about any early DC character you can think of.
Or like they'll get credit for shyt years later as if they originated when really all the new school readers are just too young to know who was the real OG.
Like ppl will say Hawkeye is biting Green Arrow, cause they don't know why Green Arrow has
Green in front of his name in the first place.
By the time DC made him in 41 there was already an Arrow out. He was just called "Arrow". And he had been out for years before Green Arrow was even thought of. So the new nikka had to add something to his name cause he was the knock off. Thats where the
Green comes from.
http://en.wikipedia.org/wiki/Arrow_(comics)