The sad truth about the survival of our historical sources is that its just a matter of luck. What survives the night of times and what not its just that, luck. But maybe the most important reason in this particular case is the Macedonian origin of Aristotle. After the death of Alexander the anti Macedonian sentiment in Athens was at its peak, and even after that Aristotle's teaching never quite fit the philosophy of that era, nor was popular among the Romans which were the ones that preserve most of the Greek philosophy. The reason that we have some of his teaching is because the Byzantine preserve some of his works and after them the Arabs found in him a philosophy that matched with their world view. Fast forward a few centurys and the Arab and Jew presence in the Spanish Peninsula with their thriving philosophical school (Maimonides for example) help reintroduce the Aristotelian thought in Western Europe.