There is a phenomenon many people at the precipice of scientific progress are privy to.
All throughout history there are examples of people arriving to sudden insights independently of each other, and sometimes seemingly at about the same time.
There have been possible explanations, like inception, or mind reading in such a way that plagiarizes. However, a more likely situation is that the idea had been waiting for the right mental or/& other context to be born.
When it happens at the same time to people who had been in correspondence with each other, another explanation that is very plausible is that credit was not given where it was due, perhaps because the “plagiarizer” (perceived credit hoarder) considered the idea not to belong to anyone, not even the “plagiarizer”, but instead to belong to the context that/who birthed it, for which they do not take credit.
Imagine how much more advanced we would be if we did not need the credit for saying/seeing something about a situation we did not create. Imagine how much more progress we would’ve made by now. But first, define “advanced” and “progress”.