It's been kanames intention to die in the end since the start, I thought that is the one thing both zeki's and yumi's agreed on. Every thing supports this, kaname turning every one into his enemy, pushing yuuki away, sowing seeds of anger and hatred inside zero. Kanames final endgame is to die, but he is taking all the pb's except yuuki with him. Kaname as the king is not able to allow him self to die till he removes the taint from his kingdom ensuring a future for both his human and vampire citizens, the taint is the pb's and the final taint in his eyes is him self.
What yuuki and zero are suppose to do is ruin his endgame and stop him from killing the pb's and him self. If kaname dies he wins even if some pb's are still alive.
Kaname is a king in the truest since, he will stain his hands red even with the blood of the Innocent if it means his kingdom survives. Most people don't like to see a king in such a way but it is some thing that is required for a king to ensure his kingdom lives on.