I read a blog that was responding to the basic question...not why was Jesus born but why did God choose to have him be born in 1st century Palestine...why would he choose that place and time? Although I must admit that I have pondered the question myself, and I do know part of the explanation offered (the part about Alexander the Great...even though he leaves out one crucial point...because of Alexander, the conquered world spoke Greek and so there was a universal language to be used)...the blogger does give a thoughtful answer:
...Thus, it is pure speculation to venture a guess as to why God did what
God did at the time that God did it. God’s ways may be entirely
arbitrary, but I think not. So in instances like this, I am often drawn to the aesthetics of the situation.
Was there something so beautiful about that time and that place that it
appealed to God? I think that may be the case. The Roman Empire, while
not nearly as revolutionary in terms of art or literature as the Greek
Empire that predated it, did curate beauty in a way previously unknown.
The reason that we still study Rome, and visit it, is that the Empire
collected and guarded much that was beautiful in the world. Ultimately,
that was fused with Christian theology, generating much that we treasure
about our tradition today. Alas, the power and violence of Rome
eventually suffused across Christianity as well.
Take a moment and read his entire answer here...