The Greek philosopher Epicurus did produce over 300 books, treatises and studies during his lifetime. Of these, only three short private letters and a few fragments do remain. On the other hand, of the works of the Greek philosopher Aristotle there does exist hundreds and hundreds of pages of speculation on all kinds of things between heaven and earth.
Similarly, nearly all of the works of Anaxagoras, who dramatically revolutionized Greek philosophy, have been lost, but the works of Plato have been extremely well preserved. Why is that? The simple answer is that the Christian Church, which took over the Roman empire in the fourth century, did like Aristotle and Plato, and it did dislike Epicurus and Anaxagoras.
Christians did strongly dislike also many other Greek philosophers. From works there often remains just small fragments or even just mentions in the works of those Greek philosophers that were sanctioned by the church. Much of this material would have been lost anyway. In those times, the old books just needed regular new copying, when the old versions started to decay. One can well argue that only the ones that would be of interest to somebody would have been preserved anyhow.
Here comes my main point. If Christians would not have taken over the Roman Empire and they would not have thoroughly erased all other religions and philosophical schools from its realms, there would certainly have been an extraordinarily different situation concerning also many of the earliest documents which did contain the seeds of rational thinking.
This is naturally just pure speculation. However, if Epicurean communities were allowed to continue to exist even after the onslaught of Christian domination in the fourth century, they would undoubtedly have existed for much longer time. In fact, nobody can honestly say if some of them would exist today. These communities would also have had an extremely strong interest in preserving the words of their master and other thinkers who supported a similar way of thinking.
The main reason why this did not happen was of course the total intolerance of the victorious Christians. In hundred years, they totally eradicated the old Roman religion and dozens of other religions and philosophical schools.
They did it such with such force, that these ideas were not left lingering even in the remotest villages in the corners of the empire. All competing belief-systems were just annihilated from the Empire of Rome. This includes also all of the earlier, rival versions of Christianity.
The victorious version of Christianity then promulgated their favorite Greek philosophers or Aristotle and Plato as ‘the great Greek philosophers’, while most of the others were hardly seen as worth a mention. This idea was cemented during the following millennium of Christian rule in Europe.
The idea of Aristotle and Plato as the special ‘great philosophers’ was funnily enough eagerly adopted even by the Muslims. Also they soon saw how the ideas of these philosophers could support their religious ideology, but the ideas of the most of the classic Greek philosophers did not fit in as neatly.
It was in the end the work of the Christian Church to promote Plato and Aristotle and belittle almost all other great Greek philosophers of the Greek Golden Age. As we have no access to the works of Epicurus and many others, we simply can not know how they would have outshone these favorites of the Church in the eyes of the modern man.
The other unfortunate consequence of all this is that the Aristotelian and Platonic philosophies soon did become the things that all other ideas were compared with, even if they did contain the same extremely flawed thinking. In the end, they were promoted to the position of the official philosophers of the church. Of course, also some of their more incompatible texts needed also to be hidden away.
Luckily for the Church Aristotle and Plato were among the extremely rare breed among the Greek philosophers. Their philosophies did namely include an idea of god in a way that was nearly compatible with the ideas of the Church, if and when one stretches things a bit. This kind of thinking was, in fact, quite rare among the first-rate Greek philosophers of the time.
All this did lead to a situation where this, in fact, quite rare way of thinking was seen as a norm also in the field of philosophy, even if the idea of an omnipotent god found favor among very few of the best minds of the Golden Age of Greece.
Naturally we can just speculate how and where the history of philosophy would have turned, if the major works of some of the greatest Greek philosophers would have been preserved. However, one can safely assume that the role or Aristotle and Plato did play in the later development of philosophy would have been very, very different.