Greek was in wide usage as the lingua franca of the Near East. It also has the benefit of actually surviving Roman rule, in the same capacity, all the way till the Late Antiquity. The Romans themselves read and spoke Greek. Thus, Greek works have had a much greater chance of surviving simply from a great, wider, and more durable distribution.
The Etruscan language, on the other hand, was never that widespread. It also reached its height much earlier than Greek; most surviving Etruscan dates from around 700 B.C. Having been conquered by Rome since the third century B.C., the Etruscan heartland was completely subsumed into the Latin civilisation at time when Greece was thriving.
The Etruscan language had largely gone extinct by the time of Claudius. Apart from perhaps some priests/scholars, Etruscan works would have been unintelligible to almost anyone who might possess Greek books.
Given the highly limited, if not outright extinct, readership, it is unsurprising that Etruscan literature were mostly lost. It would happen both from natural attrition over the centuries, as well as in the ravages of Late Antiquity wars in Italy. The (better preserved) religious Etruscan texts were lost in warfare around the same time.
So in summary:
- Written Etruscan is confined to more ancient, and shorter, times than Greek
- Etruscan was not nearly as widely spoken
- Etruscan actually went extinct
- Etruscan texts were more exposed to destructive forces