Other parallel inventions which seeming arose out of the blue, or even accidentally, but still got invented by several people at the same time: Radar, jet engin

Other parallel inventions which seeming arose out of the blue, or even accidentally, but still got invented by several people at the same time: Radar, jet engines, computers, rocketry, light bulbs, just off the top of my head. There's that old saying: "An idea whose time has come." which tends to explain things.