Who is it who has been pulling on the reins on N.Korea?
Currently, Hu is part of a collective leadership. As such, his power is checked by Jiang's cronies. But this kind of crisis provides an window of opportunity for him to hit Jiang's faction by marshalling public anger to mobilize party grassroot. A major political crisis is always a force multiplier.:)
He may not topple Jiang's faction outright but he can cut down its size.