YAY!
OK, I have two explanations:
1) What I actually believe: Jesus was an Avatar
*, come to break the Jews out of their legalism. Had nothing whatsoever to do with the actual God of the Jews, hereafter called El for the sake of clarity.
2) Assuming 1 is incorrect (because thought experiments are fun! :drool
, and Jesus was actually sent by El, why did He need to sacrifice Himself to Himself to change the rules He made in the first place?
Because El is not God. El is a sidhe-deity
*, and bound by the rules of such beings. To rewrite the rules of His covenant would be a Herculean feat of magic, requiring an unimaginably strong power source. One of the strongest generators of magical power is blood/ death. However, it's also one of the most unstable and easily tainted. An immense blood sacrifice was required, but an unwilling one would taint the "juice" and warp the shaping. So, what's a deity to do? Create the perfect sacrificial lamb. El incarnated a piece of Himself to be said perfect sacrifice.
Weird eough for ya? LOL
* Explanations can be found here.