(A) just tells us that other political systems have been different from the one present in ancient Athens. But we have no reason to think there was anything about ancient Athens’ political system that allowed for intellectual progress in the absence of stability.

This doesn’t help differentiate ancient Athens from other cities/countries. Also, we have no reason to think that holding intellectually-accomplished people in high esteem would somehow allow for intellectual progress in times of instability.

This shows how ancient Athens was different from the typical city/country in a way that helped intellectual progress. Intellectual activities had a source of money in Athens that, for others, wasn’t available in unstable times. This could have helped intellectual progress.

Even if intellectual advances lead to stability, how was ancient Athens able to achieve those intellectual advances when there was no stability? Learning what intellectual advances lead to doesn’t help explain how those advances could have come about in the first place.

We still don’t know why ancient Athens was able to make intellectual progress during a period of instability. The number of other famous philosophers and scientists has no bearing on what makes ancient Athens an exception to the general rule about the conditions for progress.