I think it's because Asians have a cultural preference for stability, experience, and old age. See Confucius.
I think that is part of it. Particularly among older Asians there tends to be a desire for tradition, continuity and experience. They are more likely to support the candidate which they feel is a proven commodity. The Clintons made an effort to court the Asian-American community during Bill's Presidency and he appointed several Asians to his administration, most notably Norman Mineta. Hillary benefits from the built up good will. I also think that because of the emphasis on tradition, there may be less resistance to the idea of a "political dynasty" than among other groups. Unfortunately, it is also true that some older Asians are prejudiced against African-Americans. But Hawaii has a majority Asian population and native son Barack Obama is wildly popular there.
Younger Asians are often divided between following their parents traditional ways and rebelling. I think there is about an equal proportion of both with the traditionalists probably supporting Hillary and the non-conformists more likely to back Obama.
I also wanted to mention within the Asian-American community there are various subdivides. For instance, Vietnamese-Americans tend to be more Republican because the party is seen as being more anti-communist. Other Asians trend more Democratic.
