Consider the invention of the airplane. The Wrights certainly invented it, but if you take a good look at what the other experimenters were doing, it's a pretty good bet that others would have gotten the pieces together in probably another 5 years.
(The Wrights succeeded arguably because they had the first directed research & development program, while the others basically just bumbled about trying things in a seat-of-the-pants manner. None of them, for example, seem to have done any calculation of how much wing area was needed or how much power was required.)
On the other hand, consider how vaccination was invented or any other "accidental" discovery/invention.
I'm aware that there are inventions that even happen at almost exactly the same time, especially when the research on the subject is ripe enough.
But when chance is a factor or the subject is not researched enough (or at all) then the confidence of an hypothesized invention happening in a close timeframe to the actual invention diminishes greatly.
(The Wrights succeeded arguably because they had the first directed research & development program, while the others basically just bumbled about trying things in a seat-of-the-pants manner. None of them, for example, seem to have done any calculation of how much wing area was needed or how much power was required.)