Answer:
Because they have conquered Constantinople, where most of these texts were preserved. But, not only Constantinople, but many other important cultural centers, such as Nicaea, Antioch, etc.
Explanation:
When the Ottomans captured Constantinople in 1453, they managed to capture all the wealth that was preserved there. Among the other things, they have captured a large cultural treasure, that was kept there for centuries. That of course included texts, manuscript from the Ancient period.
