Actually, it was one of the Church Fathers who speculated on this,quote
"Expressing his viewpoint, third century theologian Origen wrote: “It would have hindered Jesus’ teaching
from being spread through the whole world if there had been many kingdoms . . . because men everywhere would have been compelled to do military service and to fight in defence of their own land. . . . Accordingly, how could this teaching, which preaches peace and does not even allow men to take vengeance on their enemies, have had any success unless the international situation had everywhere been changed and a milder spirit prevailed at the advent of Jesus?”
and the article said it was a possibility. So blame it on the Church Fathers.