Actually there were 3 major factors that all lined up at the same time which made the time that Jesus appeared the perfect or most oportune time in history.
First, the greek culture had spread over most of the known world at that time and along with the greek culture came it's language. By the time Jesus appeared, most Jews spoke Greek along with the non-Jews, so this was the closest that the civilized world had ever been to a common language since the Tower of Babel.
Second, the Greek language is the most descriptive language known and if you were going to convey information from a creator (Jesus) to his creation, then you'ld want to employ the most acurate communication method available.
Third, the Romans had conquered this same civilized world and had built a vast network of roads for inter state commerence. It's the existance of these roads and the relative safety of the day to travel them because of the protection of the Roman army which would make the desimenation of the Gospel highly efficient. You'll find that the original apostels and diciples had sperad the Gospel to the known world in only 40 years according to the new Testament. Quite a feat for not having any cell phones, TV or automobiles.
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