Fraud is number one. (Precincts with 110% of the vote and 100% Obama, for instance).
2: He looks black. As for his heritage, that's questionable, but he was packaged and sold to American Blacks as "one of us" and they went for it, hook, line, and sinker.
3: Promises of 'free stuff'.
4: Liberal "white guilt".
5: The syncophantic media, from tingles in their legs to appraisals of how "clean" he was, Obama could do no wrong and suffered no scrutiny.
These all worked in concert with the factors you mentioned.
You are right on all counts, especially white guilt.