Illinois politics is now, and has been for at least a century, built on an amazing set of family dynasties. It's not just the Daleys, folks. Staying in Chicago, for a moment, we've got the Strogers; son Todd inherited his father John's chairmanship of the Cook County Board after his father had a stroke while in office and was incapacitated for a year in office. Beyond Chicago (partly, anyway), that Blagojevich's sister-in-law even managed to get elected to the state House of Representatives is sadly amusing enough. But then there's the Madigan family... including state Attorney General Lisa and her father Michael, the Speaker of the state House of Representatives. And that's where this little bit of sinecure and dynasticism becomes even more dysfunctional... because Blagojevich and Michael Madigan hate each other and can't work together. Madigan has long had control over the state party mechanisms.
Personally, I think appointing Roland Burris was an intentional kick in the nuts to Madigan, both on the family basis (Lisa Madigan was one of several candidates bruited about for Obama's seat in the US Senate, despite her minimal qualifications... but then minimal qualifications seem par for the course around here) and to the party leadership for pushing the impeachment process instead of showing party loyalty. "I'll appoint a black guy who can't possibly get reelected to the seat in 2010! That'll teach those bastards a lesson!"
It's all about spite, ego, self-aggrandizement, and tactics typically found at second-grade recess. It's been that way in the US Senate, too, but of different varieties; at least there hasn't been as much pouting and I'll-take-my-ball-and-go-home there, so maybe they're fifth-graders.