Why was part of the Bible written in Greek?

 
“The sacred pronouncements of God” were entrusted to the Jews, stated the apostle Paul. (Romans 3:1, 2) Hence, the first part of the Bible was written mostly in Hebrew, the Jews’ language. Yet, the Christian Scriptures were written in Greek. Why so?
 
In the fourth century B.C.E., the soldiers who served under Alexander the Great spoke various dialects of classical Greek, which were in the process of being blended to form Koine, or common Greek. Alexander’s conquests contributed to Koine becoming the international language of the day. By the time of those conquests, the Jews had become widely dispersed. Many never returned to Palestine from their Babylonian exile, which had ended centuries earlier. As a result, many of the Jews eventually lost their grasp of pure Hebrew and used Greek instead. (Acts 6:1) For their benefit, the Septuagint, a Koine, or common Greek, translation of the Hebrew Scriptures, was produced.
 

The Dictionnaire de la Bible notes that no other language had “the richness, the flexibility, and the universal and international character of Greek.” With its extensive and exact vocabulary, detailed grammar, and verbs that aptly expressed subtle shades of meaning, it was “a language of communication, of circulation, of propagation—precisely the language needed by Christianity.” Is it not fitting that Greek was the language in which the Christian message was penned?