Someone had the idea
It's hard to tell who was first to invent the telephone, Alexander Graham Bell or Elisha Gray. Thomas Edison wasn't the first to make light glow in a glass bulb. James Kirby had the idea for a bagless vacuum long before James Dyson.
It's always possible that someone did steal an idea and the winner wrote the history book. It’s also possible that the “first” person's work was unknown to the public eye or that their idea wasn't developed enough.
Behind every genius creation there's a guy in the background saying, “Hey that guy stole my idea.”
