I don't find it surprising that Hatoyama fell; what I find more surprising is how poor a politician he turned out to be. He set himself up for failure on the Okinawa issue, and he managed to get involved in shady financial dealings after the DPJ's victory suggested the Japanese public had had their fill of corrupt back-room politics.
Kan seems a breath of fresh air in Japanese politics even if he's older than me. He has a rather non-traditional resume and isn't the offspring of another politician.
Oh well, if they run out of options,
Koizumi can always swoop in.