* Alexander the Great's conquests: In the 4th century BC, Alexander the Great conquered a vast territory from Greece to Persia. His campaigns spread Greek culture, language, and administration throughout the region. This led to the widespread adoption of Koine Greek, a common dialect of Greek, as a lingua franca (common language) in the eastern Mediterranean.
* Roman rule: When the Romans conquered the area, they continued to use Koine Greek as the language of administration and commerce. This further solidified Greek as the dominant language in the region.
* Trade and communication: Greek was already a language used for trade and communication across the Mediterranean. The expansion of the Roman Empire and the subsequent trade networks made Greek even more prevalent.
So, while no single person ordered the people of the first century to speak Greek, a combination of historical factors, including conquests, administrative use, and trade, made Greek the dominant language of the eastern Mediterranean.
It's important to remember that while Greek was the dominant language, other languages continued to be spoken. Hebrew was still spoken by the Jewish population, for example, and Aramaic was also common in some areas.