Several things may be gathered out of Luke 2:1-7 that reveal to us that it was the proper time for the Savior to come. First, Jesus was born in the days of Augustus Caesar, when the Roman empire extended itself further than ever before or since, from Parthia to Britain, so that it was then called Terraram orbis imperium, the empire of the whole earth. Here, the Roman Empire is called all the world (v. 1), since there was scarcely any part of the civilized world that wasn't dependent on it.
Now, this was the time when the Messiah was to be born according to Daniel’s prophecy (Daniel 2:44): In the days of those kings the God of heaven will set up a kingdom which will never be destroyed, and that kingdom will not be left for another people.
Second, He was born when Judea had become a province of the empire. When all the Roman empire was taxed, the Jews were taxed among the rest. Jerusalem was taken by Pompey the Roman general, about sixty years before this, who granted the government of the church to Hyrcanus, but not the government of the state. By degrees, it was more and more reduced until Judea was ruled by Cyrenius (Sulpitius Quirinus) the Roman governor of Syria (v. 2). This was the exact time the Messiah was to be born, as given in dying Jacob’s prophecy, that Shiloh should come when the scepter was departed from Judah and the lawgiver from between his feet (Genesis 49:10).
There is another circumstance implied in this general enrollment of all the subjects of the empire, which is, that there was now universal peace in the empire. The temple of Janus was now shut, which signaled that there were no wars raging - and now it was fit for the Prince of peace to be born.
Adapted from Matthew Henry's Commentary on the Whole Bible (Luke 2).