[Nogbad]

With regard to the Syrian connection,
this is what the Oxford History of Islam states:

(Omar) launched one set of offensives
against the Byzantine controlled territores of Palestine and Syria
home to many Arabic speaking tribes
(part of the primary audience to which the Quran had been addressed)

[JasonC]

The Byzantines spoke Greek, it was the official language of the orthodox church and the state administration. The primary language in Syria was Syriac, a modernized version of Aramaic. The Sassanids to the east spoke a version of Persian. In Egypt the language was Coptic, in Armenia it was classical Armenian. Arabic was spoken in Arabia and among nomad tribes in the desert fringes of the other regions, yes - who were mostly illiterate. As for written Arabic, it was practically non-existent, a few poems being about it. The Koran was not addressed to these tribes, because (1) they couldn't read a line and (2) the Koran did not yet exist as a single book. Muhammad's speeches, or oral retellings of his sayings or pronouncements, were indeed addressed to the Arab tribes, hovering on the desert outskirts of Syria, Palestine, and Mesopotamia.