>One second he's all sad about beating down Sam Jackson, and
>like a second later he practically just says, "ah hell with
>it, Palpatine I'm ya boy."
>
>The only way I could explain it was that he just thought he
>already fucked up good fashion killing the head of the Jedi,
>he might as well go all the way.

Basically that. And the fact that Lucas just needed 2 push the story along.