One general thing is that it is the most ‘classic’ works that are copied the most and most frequently. Early works in philosophy from Plato or even Aristotle are much more likely to survive than, say, philosophers from later antiquity (can you even think of many?) Of course that isn’t to say that all the most ancient philosophers’ works survived—we have little of Parmenides for example. Perhaps another reason for Plato and Aristotle to survive particularly is their relevance to Christian theology, but I don’t really buy that as we have more Plato than Aristotle but Christian theology is more Aristotelian.

A simple argument about mathematics or engineering can be made by going to Constantinople and looking at the Hagia Sophia. Much technical and practical mathematical ability would have been needed at the time to construct it but we have little interesting mathematics from that time (6th century). I find it improbable that we would have such mathematicians as Archimedes and Apollonius around 250BCE, then roughly nothing for 750 years, and then the Hagia Sophia. I find it more believable that the tradition of mathematics continued but that only those most ancient, foundational and well-regarded works were sufficiently reproduced to make it to the present. To be clear, I am not trying to claim that one needs the kind of mathematicians produced by Apollonius to build a large dome but rather that a society capable of continuing that kind of technical ability for so long ought to have also been supporting the continuation of technical mathematics.

One then has to wonder: if this work was being done in the Greek-speaking world, what did this continuation look like? Among the known works, some of Apollonius’ work was not really improved upon until Riemann over 2000 years after his death.