well, for most, the interest started with Zero's own books. As most people do with presidential candidates who are relatively unknown, people wanted to know about this person. Where did he go to school? what kind of friends did he have? what did he do with the first quarter century of his life? What did he accomplish as a senator? Who did he hang with as a senator? What did he accomplish as a community activist? What ties did he build? That kind of stuff.
And what people found over and over again was sealed records, missing records, nonexistent records, etc, and when people fought to have these records accessable, that candidate, now elected, starting spending millions (of taxpayer dollars) making those records inaccessable. That's interesting. In fact, it's unprecidentedly interesting.
Now you add all that together with the no people, questionable people, hidden people, downright strange people this candidate, now elected, has surrounded or denied surrounding himself with, or continues to surround himself with (galpal Valerie Jarret, anyone?), coupled with Zero's apparent inability to stay in one place more than two days, and it's practically Stephen King level interesting.
fyi, a related article:
http://www.freerepublic.com/focus/f-news/2296157/posts