But how could people ascribe a heavenly “pre-existence” to a real human and mortal figure of recent history? To understand this, you have to enter into the “logic” of ancient theological thought, and especially “apocalyptic” thought. I’ll sketch it briefly. God doesn’t make up his game-plan as the game goes along, but has the plan (of world history, redemption, judgement, etc.) all laid out even before creation. So, as God acts in revelation, each action is also an unveiling of his prior purpose and plan. So, “eschatological” events were actually in God’s purpose from the beginning: “final things = first things” (to paraphrase a scholarly formula).
http://larryhurtado.wordpress.com/2014/05/15/jesus-pre-existence-etc-responding-to-questions/