^Like I said, different writers independently coming up with the same idea only seems unlikely to people who aren't writers -- or producers or editors taking submissions from writers. Not only is it not improbable or suspicious, it is downright routine. It happens all the time. There are only so many ways to put a story together coherently, and we're all part of the same culture with the same ideas influencing us.
There are over 700 distinct Star Trek
episodes and movies at this point. You can probably pick any given one of them and find an existing story that it closely parallels.