GMAT Sentence Correction (SC) | Re: It was the coincidence of the geographic range of the sickle

Can you please explain this. Specially I am not able to understand the thing about why there need to be two distinct entities?

It was coincidence of time that Einstien and Max Plank both researched on Particle Physics.

This suggests that Einstien and Max Plank both researched Particle Physics at the same time.

Here also, it says It was the coincidence of
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